HackerRank How Many Substrings problem solution

In this HackerRank How Many Substrings problem solution, we have given a string of n characters where each character is indexed from 0 to n-1 and we have given q queries in the form of two integer indices left and right. we need to count and print the number of different substrings of string in the inclusive range between left and right.

Problem solution in Java.

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.InputMismatchException;
import java.util.List;

public class How_Many_Substrings {
    InputStream is;
    PrintWriter out;
    String INPUT = "";
    
    void solve()
    {
        int n = ni(), Q = ni();
        char[] s = ns(n);
        int[][] qs = new int[Q][];
        for(int z = 0;z < Q;z++){
            qs[z] = new int[]{ni(), ni(), z};
        }
        Arrays.sort(qs, new Comparator<int[]>() {
            public int compare(int[] a, int[] b) {
                return a[1] - b[1];
            }
        });

        SuffixAutomatonOfBit sa = SuffixAutomatonOfBit.build(s);
        sa.sortTopologically();
        SuffixAutomatonOfBit.Node[] nodes = sa.nodes;
        int[] from = new int[nodes.length-1];
        int[] to = new int[nodes.length-1];
        int p = 0;
        for(SuffixAutomatonOfBit.Node node : nodes){
            if(node.id >= 1){
                from[p] = node.link.id; to[p] = node.id; p++;
            }
        }
        assert p == nodes.length-1;
        int[][] g = packU(nodes.length, from, to);
        int[][] pars = parents3(g, 0);
        int[] par = pars[0], ord = pars[1], dep = pars[2];
        HeavyLightDecomposition hld = new HeavyLightDecomposition(g, par, ord, dep);
        int m = hld.cluspath.length;
        SegmentTreeOverwrite[] sts = new SegmentTreeOverwrite[m];
        for(int i = 0;i < m;i++){
            sts[i] = new SegmentTreeOverwrite(hld.cluspath[i].length);
        }
        
        int[] base = new int[n];
        int qp = 0;
        int np = 0;
        long[] ft0 = new long[n+3];
        long[] ft1 = new long[n+3];
        long[] ans = new long[Q];
        for(int i = 0;i < n;i++){
            while(!(nodes[np].len == i+1 && nodes[np].original == null))np++;
            base[i] = np;
//            tr("base", base[i]);
            
            // 5 3 1 0
            // 5 3 1 0
            // 8 6 3 1 0 ?
            // aaba
            
            // delete
            int cur = 0;
            int ppos = 0;
            while(true){
                int last = sts[hld.clus[cur]].get(hld.clusiind[cur]);
                if(last == -1)break;
                int lca = hld.lca(base[last], base[i]);
                // delete from lca to cur
    //            nodes[cur].len, nodes[lca].len;
                int inf = last-nodes[lca].len+1;
                int sup = last-ppos+1;
//                tr("del", last, ppos, nodes[lca].len, inf, sup);
                // _/
                addFenwick(ft0, 0, -(sup-inf));
                addFenwick(ft0, sup+1, +(sup-inf));
                addFenwick(ft0, inf+1, -(inf+1));
                addFenwick(ft0, sup+1, +inf+1);
                addFenwick(ft1, inf+1, 1);
                addFenwick(ft1, sup+1, -1);
//                tr(i, restoreRangeFenwick(ft0, ft1));
                ppos = nodes[lca].len;
                assert dep[base[i]]-dep[lca]-1 >= 0;
                cur = hld.ancestor(base[i], dep[base[i]]-dep[lca]-1);
            }
            // x
            //b a
            //   a
            
            // paint
            int cx = hld.clus[base[i]]; // cluster
            int ind = hld.clusiind[base[i]]; // pos in cluster
            while(true){
                sts[cx].update(0, ind+1, i);
                int con = par[hld.cluspath[cx][0]];
                if(con == -1)break;
                ind = hld.clusiind[con];
                cx = hld.clus[con];
            }
            
//            tr(i, restoreRangeFenwick(ft0, ft1));
            addFenwick(ft0, 0, i+1+1);
            addFenwick(ft0, i+1+1, -(i+1+1));
            addFenwick(ft1, 0, -1);
            addFenwick(ft1, i+1+1, 1);
//            tr(i, restoreRangeFenwick(ft0, ft1));
            
            while(qp < Q && qs[qp][1] <= i){
//                tr(qs[qp]);
                ans[qs[qp][2]] = sumRangeFenwick(ft0, ft1, qs[qp][0]);
                qp++;
            }
        }
        for(long an : ans){
            out.println(an);
        }
    }
    
    public static long sumFenwick(long[] ft, int i)
    {
        long sum = 0;
        for(i++;i > 0;i -= i&-i)sum += ft[i];
        return sum;
    }
    
    public static void addFenwick(long[] ft, int i, long v)
    {
        if(v == 0)return;
        int n = ft.length;
        for(i++;i < n;i += i&-i)ft[i] += v;
    }
    
    public static int firstGEFenwick(long[] ft, long v)
    {
        int i = 0, n = ft.length;
        for(int b = Integer.highestOneBit(n);b != 0;b >>= 1){
            if((i|b) < n && ft[i|b] < v){
                i |= b;
                v -= ft[i];
            }
        }
        return i;
    }
    
    public static long[] restoreFenwick(long[] ft)
    {
        int n = ft.length-1;
        long[] ret = new long[n];
        for(int i = 0;i < n;i++)ret[i] = sumFenwick(ft, i);
        for(int i = n-1;i >= 1;i--)ret[i] -= ret[i-1];
        return ret;
    }
    
    public static int findGFenwick(long[] ft, long v)
    {
        int i = 0;
        int n = ft.length;
        for(int b = Integer.highestOneBit(n);b != 0 && i < n;b >>= 1){
            if(i + b < n){
                int t = i + b;
                if(v >= ft[t]){
                    i = t;
                    v -= ft[t];
                }
            }
        }
        return v != 0 ? -(i+1) : i-1;
    }
    
    public static long[] buildFenwick(long[] a)
    {
        int n = a.length;
        long[] ft = new long[n+1];
        System.arraycopy(a, 0, ft, 1, n);
        for(int k = 2, h = 1;k <= n;k*=2, h*=2){
            for(int i = k;i <= n;i+=k){
                ft[i] += ft[i-h];
            }
        }
        return ft;
    }
    
    public static void addRangeFenwick(long[] ft0, long[] ft1, int i, long v)
    {
        addFenwick(ft1, i+1, -v);
        addFenwick(ft1, 0, v);
        addFenwick(ft0, i+1, v*(i+1));
    }
    
    public static void addRangeFenwick(long[] ft0, long[] ft1, int a, int b, long v)
    {
        if(a <= b){
            addFenwick(ft1, b+1, -v);
            addFenwick(ft0, b+1, v*(b+1));
            addFenwick(ft1, a, v);
            addFenwick(ft0, a, -v*a);
        }
    }
    
    public static long sumRangeFenwick(long[] ft0, long[] ft1, int i)
    {
        return sumFenwick(ft1, i) * (i+1) + sumFenwick(ft0, i);
    }
    
    public static long[] restoreRangeFenwick(long[] ft0, long[] ft1)
    {
        int n = ft0.length-1;
        long[] ret = new long[n];
        for(int i = 0;i < n;i++)ret[i] = sumRangeFenwick(ft0, ft1, i);
        for(int i = n-1;i >= 1;i--)ret[i] -= ret[i-1];
        return ret;
    }

    
    public static class SegmentTreeOverwrite {
        public int M, H, N;
        public int[] cover;
        public int I = Integer.MAX_VALUE;
        
        public SegmentTreeOverwrite(int len)
        {
            N = len;
            M = Integer.highestOneBit(Math.max(N-1, 1))<<2;
            H = M>>>1;
            cover = new int[M];
            Arrays.fill(cover, I);
            for(int i = 0;i < N;i++){
                cover[H+i] = -1;
            }
            for(int i = H-1;i >= 1;i--){
                propagate(i);
            }
        }
        
        private void propagate(int i){}
        
        public void update(int l, int r, int v){ update(l, r, v, 0, H, 1); }
        
        private void update(int l, int r, int v, int cl, int cr, int cur)
        {
            if(l <= cl && cr <= r){
                cover[cur] = v;
                propagate(cur);
            }else{
                int mid = cl+cr>>>1;
                if(cover[cur] != I){ // back-propagate
                    cover[2*cur] = cover[2*cur+1] = cover[cur];
                    cover[cur] = I;
                    propagate(2*cur);
                    propagate(2*cur+1);
                }
                if(cl < r && l < mid){
                    update(l, r, v, cl, mid, 2*cur);
                }
                if(mid < r && l < cr){
                    update(l, r, v, mid, cr, 2*cur+1);
                }
                propagate(cur);
            }
        }
        
        public int get(int x){ 
            int val = I;
            for(int i = H+x;i >= 1;i>>>=1){
                if(cover[i] != I)val = cover[i];
            }
            return val;
        }
    }

    
    public static class HeavyLightDecomposition {
        public int[] clus;
        public int[][] cluspath;
        public int[] clusiind;
        public int[] par, dep;
        
        public HeavyLightDecomposition(int[][] g, int[] par, int[] ord, int[] dep)
        {
            init(g, par, ord, dep);
        }
        
        public void init(int[][] g, int[] par, int[] ord, int[] dep)
        {
            clus = decomposeToHeavyLight(g, par, ord);
            cluspath = clusPaths(clus, ord);
            clusiind = clusIInd(cluspath, g.length);
            this.par = par;
            this.dep = dep;
        }
        
        public static int[] decomposeToHeavyLight(int[][] g, int[] par, int[] ord)
        {
            int n = g.length;
            int[] size = new int[n];
            Arrays.fill(size, 1);
            for(int i = n-1;i > 0;i--)size[par[ord[i]]] += size[ord[i]];
            
            int[] clus = new int[n];
            Arrays.fill(clus, -1);
            int p = 0;
            for(int i = 0;i < n;i++){
                int u = ord[i];
                if(clus[u] == -1)clus[u] = p++;
                // centroid path (not heavy path)
                int argmax = -1;
                for(int v : g[u]){
                    if(par[u] != v && (argmax == -1 || size[v] > size[argmax]))argmax = v;
                }
                if(argmax != -1)clus[argmax] = clus[u];
            }
            return clus;
        }
        
        public static int[][] clusPaths(int[] clus, int[] ord)
        {
            int n = clus.length;
            int[] rp = new int[n];
            int sup = 0;
            for(int i = 0;i < n;i++){
                rp[clus[i]]++;
                sup = Math.max(sup, clus[i]);
            }
            sup++;
            
            int[][] row = new int[sup][];
            for(int i = 0;i < sup;i++)row[i] = new int[rp[i]];
            
            for(int i = n-1;i >= 0;i--){
                row[clus[ord[i]]][--rp[clus[ord[i]]]] = ord[i];
            }
            return row;
        }
        
        public static int[] clusIInd(int[][] clusPath, int n)
        {
            int[] iind = new int[n];
            for(int[] path : clusPath){
                for(int i = 0;i < path.length;i++){
                    iind[path[i]] = i;
                }
            }
            return iind;
        }
        
        public int lca(int x, int y)
        {
            int rx = cluspath[clus[x]][0];
            int ry = cluspath[clus[y]][0];
            while(clus[x] != clus[y]){
                if(dep[rx] > dep[ry]){
                    x = par[rx];
                    rx = cluspath[clus[x]][0];
                }else{
                    y = par[ry];
                    ry = cluspath[clus[y]][0];
                }
            }
            return clusiind[x] > clusiind[y] ? y : x;
        }
        
        public int ancestor(int x, int v)
        {
            while(x != -1){
                if(v <= clusiind[x])return cluspath[clus[x]][clusiind[x]-v];
                v -= clusiind[x]+1;
                x = par[cluspath[clus[x]][0]];
            }
            return x;
        }
    }

    
    public static int lca2(int a, int b, int[][] spar, int[] depth) {
        if (depth[a] < depth[b]) {
            b = ancestor(b, depth[b] - depth[a], spar);
        } else if (depth[a] > depth[b]) {
            a = ancestor(a, depth[a] - depth[b], spar);
        }

        if (a == b)
            return a;
        int sa = a, sb = b;
        for (int low = 0, high = depth[a], t = Integer.highestOneBit(high), k = Integer
                .numberOfTrailingZeros(t); t > 0; t >>>= 1, k--) {
            if ((low ^ high) >= t) {
                if (spar[k][sa] != spar[k][sb]) {
                    low |= t;
                    sa = spar[k][sa];
                    sb = spar[k][sb];
                } else {
                    high = low | t - 1;
                }
            }
        }
        return spar[0][sa];
    }

    protected static int ancestor(int a, int m, int[][] spar) {
        for (int i = 0; m > 0 && a != -1; m >>>= 1, i++) {
            if ((m & 1) == 1)
                a = spar[i][a];
        }
        return a;
    }

    public static int[][] logstepParents(int[] par) {
        int n = par.length;
        int m = Integer.numberOfTrailingZeros(Integer.highestOneBit(n - 1)) + 1;
        int[][] pars = new int[m][n];
        pars[0] = par;
        for (int j = 1; j < m; j++) {
            for (int i = 0; i < n; i++) {
                pars[j][i] = pars[j - 1][i] == -1 ? -1 : pars[j - 1][pars[j - 1][i]];
            }
        }
        return pars;
    }

    
    public static int[][] parents3(int[][] g, int root) {
        int n = g.length;
        int[] par = new int[n];
        Arrays.fill(par, -1);

        int[] depth = new int[n];
        depth[0] = 0;

        int[] q = new int[n];
        q[0] = root;
        for (int p = 0, r = 1; p < r; p++) {
            int cur = q[p];
            for (int nex : g[cur]) {
                if (par[cur] != nex) {
                    q[r++] = nex;
                    par[nex] = cur;
                    depth[nex] = depth[cur] + 1;
                }
            }
        }
        return new int[][] { par, q, depth };
    }

    
    static int[][] packU(int n, int[] from, int[] to) {
        int[][] g = new int[n][];
        int[] p = new int[n];
        for (int f : from)
            p[f]++;
        for (int t : to)
            p[t]++;
        for (int i = 0; i < n; i++)
            g[i] = new int[p[i]];
        for (int i = 0; i < from.length; i++) {
            g[from[i]][--p[from[i]]] = to[i];
            g[to[i]][--p[to[i]]] = from[i];
        }
        return g;
    }
    
    public static class SuffixAutomatonOfBit {
        public Node t0;
        public int len;
        public Node[] nodes;
        public int gen;
        private boolean sortedTopologically = false;
        private boolean lexsorted = false;
        
        private SuffixAutomatonOfBit(int n)
        {
            gen = 0;
            nodes = new Node[2*n];
            this.t0 = makeNode(0, null);
        }
        
        private Node makeNode(int len, Node original)
        {
            Node node = new Node();
            node.id = gen;
            node.original = original;
            node.len = len;
            nodes[gen++] = node;
            return node;
        }
        
        public static class Node
        {
            public int id;
            public int len;
            public char key;
            public Node link;
            private Node[] next = new Node[3];
            public Node original;
            public int np = 0;
            public int hit = 0;
            
            public void putNext(char c, Node to)
            {
                to.key = c;
                if(hit<<~(c-'a')<0){
                    for(int i = 0;i < np;i++){
                        if(next[i].key == c){
                            next[i] = to;
                            return;
                        }
                    }
                }
                hit |= 1<<c-'a';
                if(np == next.length){
                    next = Arrays.copyOf(next, np*2);
                }
                next[np++] = to;
            }
            
            public boolean containsKeyNext(char c)
            {
                return hit<<~(c-'a')<0;
//                for(int i = 0;i < np;i++){
//                    if(next[i].key == c)return true;
//                }
//                return false;
            }
            
            public Node getNext(char c)
            {
                if(hit<<~(c-'a')<0){
                    for(int i = 0;i < np;i++){
                        if(next[i].key == c)return next[i];
                    }
                }
                return null;
            }
            
            public List<String> suffixes(char[] s)
            {
                List<String> list = new ArrayList<String>();
                if(id == 0)return list;
                int first = original != null ? original.len : len;
                for(int i = link.len + 1;i <= len;i++){
                    list.add(new String(s, first - i, i));
                }
                return list;
            }
        }

        public static SuffixAutomatonOfBit build(char[] str)
        {
            int n = str.length;
            SuffixAutomatonOfBit sa = new SuffixAutomatonOfBit(n);
            sa.len = str.length;
            
            Node last = sa.t0;
            for(char c : str){
                last = sa.extend(last, c);
            }
            
            return sa;
        }
        
        public Node extend(Node last, char c)
        {
            Node cur = makeNode(last.len+1, null);
            Node p;
            for(p = last; p != null && !p.containsKeyNext(c);p = p.link){
                p.putNext(c, cur);
            }
            if(p == null){
                cur.link = t0;
            }else{
                Node q = p.getNext(c); // not null
                if(p.len + 1 == q.len){
                    cur.link = q;
                }else{
                    Node clone = makeNode(p.len+1, q);
                    clone.next = Arrays.copyOf(q.next, q.next.length);
                    clone.hit = q.hit;
                    clone.np = q.np;
                    clone.link = q.link;
                    for(;p != null && q.equals(p.getNext(c)); p = p.link){
                        p.putNext(c, clone);
                    }
                    q.link = cur.link = clone;
                }
            }
            return cur;
        }
        
        public SuffixAutomatonOfBit lexSort()
        {
            for(int i = 0;i < gen;i++){
                Node node = nodes[i];
                Arrays.sort(node.next, 0, node.np, new Comparator<Node>() {
                    public int compare(Node a, Node b) {
                        return a.key - b.key;
                    }
                });
            }
            lexsorted = true;
            return this;
        }
        
        public SuffixAutomatonOfBit sortTopologically()
        {
            int[] indeg = new int[gen];
            for(int i = 0;i < gen;i++){
                for(int j = 0;j < nodes[i].np;j++){
                    indeg[nodes[i].next[j].id]++;
                }
            }
            Node[] sorted = new Node[gen];
            sorted[0] = t0;
            int p = 1;
            for(int i = 0;i < gen;i++){
                Node cur = sorted[i];
                for(int j = 0;j < cur.np;j++){
                    if(--indeg[cur.next[j].id] == 0){
                        sorted[p++] = cur.next[j];
                    }
                }
            }
            
            for(int i = 0;i < gen;i++)sorted[i].id = i;
            nodes = sorted;
            sortedTopologically = true;
            return this;
        }
        
        // visualizer
        
        public String toString()
        {
            StringBuilder sb = new StringBuilder();
            for(Node n : nodes){
                if(n != null){
                    sb.append(String.format("{id:%d, len:%d, link:%d, cloned:%b, ",
                            n.id,
                            n.len,
                            n.link != null ? n.link.id : null,
                            n.original.id));
                    sb.append("next:{");
                    for(int i = 0;i < n.np;i++){
                        sb.append(n.next[i].key + ":" + n.next[i].id + ",");
                    }
                    sb.append("}");
                    sb.append("}");
                    sb.append("n");
                }
            }
            return sb.toString();
        }
        
        public String toGraphviz(boolean next, boolean suffixLink)
        {
            StringBuilder sb = new StringBuilder("http://chart.apis.google.com/chart?cht=gv:dot&chl=");
            sb.append("digraph{");
            for(Node n : nodes){
                if(n != null){
                    if(suffixLink && n.link != null){
                        sb.append(n.id)
                        .append("->")
                        .append(n.link.id)
                        .append("[style=dashed],");
                    }
                    
                    if(next && n.next != null){
                        for(int i = 0;i < n.np;i++){
                            sb.append(n.id)
                            .append("->")
                            .append(n.next[i].id)
                            .append("[label=")
                            .append(n.next[i].key)
                            .append("],");
                        }
                    }
                }
            }
            sb.append("}");
            return sb.toString();
        }
        
        public String label(Node n)
        {
            if(n.original != null){
                return n.id + "C";
            }else{
                return n.id + "";
            }
        }
        
        public String toDot(boolean next, boolean suffixLink)
        {
            StringBuilder sb = new StringBuilder("digraph{n");
            sb.append("graph[rankdir=LR];n");
            sb.append("node[shape=circle];n");
            for(Node n : nodes){
                if(n != null){
                    if(suffixLink && n.link != null){
                        sb.append(""" + label(n) + """)
                        .append("->")
                        .append(""" + label(n.link) + """)
                        .append("[style=dashed];n");
                    }
                    
                    if(next && n.next != null){
                        for(int i = 0;i < n.np;i++){
                            sb.append(""" + label(n) + """)
                            .append("->")
                            .append(""" + label(n.next[i]) + """)
                            .append("[label="")
                            .append(n.next[i].key)
                            .append(""];n");
                        }
                    }
                }
            }
            sb.append("}n");
            return sb.toString();
        }
    }
    
    void run() throws Exception
    {
        is = INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes());
        out = new PrintWriter(System.out);
        
        long s = System.currentTimeMillis();
        solve();
        out.flush();
        if(!INPUT.isEmpty())tr(System.currentTimeMillis()-s+"ms");
    }
    
    public static void main(String[] args) throws Exception { 
        new How_Many_Substrings().run(); 
    }
    
    private byte[] inbuf = new byte[1024];
    public int lenbuf = 0, ptrbuf = 0;
    
    private int readByte()
    {
        if(lenbuf == -1)throw new InputMismatchException();
        if(ptrbuf >= lenbuf){
            ptrbuf = 0;
            try { lenbuf = is.read(inbuf); } catch (IOException e) { throw new InputMismatchException(); }
            if(lenbuf <= 0)return -1;
        }
        return inbuf[ptrbuf++];
    }
    
    private boolean isSpaceChar(int c) { return !(c >= 33 && c <= 126); }
    private int skip() { int b; while((b = readByte()) != -1 && isSpaceChar(b)); return b; }
    
    private double nd() { return Double.parseDouble(ns()); }
    private char nc() { return (char)skip(); }
    
    private String ns()
    {
        int b = skip();
        StringBuilder sb = new StringBuilder();
        while(!(isSpaceChar(b))){ // when nextLine, (isSpaceChar(b) && b != ' ')
            sb.appendCodePoint(b);
            b = readByte();
        }
        return sb.toString();
    }
    
    private char[] ns(int n)
    {
        char[] buf = new char[n];
        int b = skip(), p = 0;
        while(p < n && !(isSpaceChar(b))){
            buf[p++] = (char)b;
            b = readByte();
        }
        return n == p ? buf : Arrays.copyOf(buf, p);
    }
    
    private char[][] nm(int n, int m)
    {
        char[][] map = new char[n][];
        for(int i = 0;i < n;i++)map[i] = ns(m);
        return map;
    }
    
    private int[] na(int n)
    {
        int[] a = new int[n];
        for(int i = 0;i < n;i++)a[i] = ni();
        return a;
    }
    
    private int ni()
    {
        int num = 0, b;
        boolean minus = false;
        while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'));
        if(b == '-'){
            minus = true;
            b = readByte();
        }
        
        while(true){
            if(b >= '0' && b <= '9'){
                num = num * 10 + (b - '0');
            }else{
                return minus ? -num : num;
            }
            b = readByte();
        }
    }
    
    private long nl()
    {
        long num = 0;
        int b;
        boolean minus = false;
        while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'));
        if(b == '-'){
            minus = true;
            b = readByte();
        }
        
        while(true){
            if(b >= '0' && b <= '9'){
                num = num * 10 + (b - '0');
            }else{
                return minus ? -num : num;
            }
            b = readByte();
        }
    }
    
    private static void tr(Object... o) { System.out.println(Arrays.deepToString(o)); }
}

Problem solution in C++.

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N = 100000 + 10;
struct Ask {
    int l, r, id;
    friend bool operator<(Ask &a, Ask &b) { return a.r < b.r; };
} ask[N];
ll ans[N];
char s[N];
// SAM
int Tr(char c) { return c - 'a'; }
int cnt, lst, a[N << 1][26], l[N << 1], f[N << 1], mrk[N << 1];
void extend(int c) {
    int p = lst;
    int np = lst = ++cnt;
    l[np] = l[p] + 1;
    mrk[np] = 1;
    while (!a[p][c] && p) a[p][c] = np, p = f[p];
    if (!p)
        f[np] = 1;
    else {
        int q = a[p][c];
        if (l[p] + 1 == l[q])
            f[np] = q;
        else {
            int nq = ++cnt;
            l[nq] = l[p] + 1;
            mrk[nq] = 0;
            memcpy(a[nq], a[q], sizeof(a[q]));
            f[nq] = f[q];
            f[np] = f[q] = nq;
            while (a[p][c] == q) a[p][c] = nq, p = f[p];
        }
    }
}
// Segment Tree
ll tag[N << 1], sum[N << 1];
int idx(int l, int r) { return l + r | l != r; }
void build(int l, int r) {
    int x = idx(l, r), mid = l + r >> 1;
    tag[x] = sum[x] = 0;
    if (l == r) return;
    build(l, mid);
    build(mid + 1, r);
}
void add_tag(int l, int r, ll v) {
    int x = idx(l, r);
    tag[x] += v;
    sum[x] += v * (r - l + 1);
}
void pd(int l, int r) {
    int x = idx(l, r), mid = l + r >> 1;
    if (tag[x]) {
        add_tag(l, mid, tag[x]);
        add_tag(mid + 1, r, tag[x]);
        tag[x] = 0;
    }
}
void up(int l, int r) {
    int mid = l + r >> 1;
    sum[idx(l, r)] = sum[idx(l, mid)] + sum[idx(mid + 1, r)];
}
void upd(int l, int r, int ul, int ur, ll v) {
    int x = idx(l, r), mid = l + r >> 1;
    if (ul <= l && r <= ur) {
        add_tag(l, r, v);
        return;
    }
    pd(l, r);
    if (ul <= mid) upd(l, mid, ul, ur, v);
    if (mid < ur) upd(mid + 1, r, ul, ur, v);
    up(l, r);
}
ll qry(int l, int r, int ql, int qr) {
    int x = idx(l, r), mid = l + r >> 1;
    if (ql <= l && r <= qr) return sum[x];
    pd(l, r);
    ll res = 0;
    if (ql <= mid) res += qry(l, mid, ql, qr);
    if (mid < qr) res += qry(mid + 1, r, ql, qr);
    return res;
}
// LCT
pair<int, int> mp[N];
int fa[N << 1], son[N << 1][2], tmp[N << 1];
int cov[N << 1], ps[N << 1], len[N << 1];
void cov1(int x, int v) {
    cov[x] = v;
    ps[x] = v;
}
void pb(int x) {
    if (cov[x]) {
        cov1(son[x][0], cov[x]);
        cov1(son[x][1], cov[x]);
        cov[x] = 0;
    }
}
void lct_up(int x) {
    if (son[x][0]) ps[x] = max(ps[x], ps[son[x][0]]);
    if (son[x][1]) ps[x] = max(ps[x], ps[son[x][1]]);
}
void rotate(int x) {
    int y = fa[x], w = son[y][1] == x;
    son[y][w] = son[x][w ^ 1];
    if (son[x][w ^ 1]) fa[son[x][w ^ 1]] = y;
    if (fa[y]) {
        int z = fa[y];
        if (son[z][0] == y)
            son[z][0] = x;
        else if (son[z][1] == y)
            son[z][1] = x;
    }
    fa[x] = fa[y];
    fa[y] = x;
    son[x][w ^ 1] = y;
    lct_up(y);
}
bool isroot(int x) { return !fa[x] || son[fa[x]][0] != x && son[fa[x]][1] != x; }
void splay(int x) {
    int s = 1, i = x, y;
    tmp[1] = i;
    while (!isroot(i)) tmp[++s] = i = fa[i];
    while (s) pb(tmp[s--]);
    while (!isroot(x)) {
        y = fa[x];
        if (!isroot(y)) {
            if ((son[fa[y]][0] == y) ^ (son[y][0] == x))
                rotate(x);
            else
                rotate(y);
        }
        rotate(x);
    }
    lct_up(x);
}
int mcnt; 
void access(int x, int v) {
    mcnt = 0;
    cov1(x, v);
    for (int y = 0; x; y = x, x = fa[x]) {
        splay(x);
        son[x][1] = y;
        mp[++mcnt] = make_pair(len[x], ps[x]);
        lct_up(x);
    }
}
int n, q;
void lct_init() {
    for (int i = 0; i <= 2 * n; ++i) {
        son[i][0] = son[i][1] = fa[i] = 0;
        ps[i] = cov[i] = 0;
    }
}
int b[N << 1], x[N << 1];
int ver[N << 1], id[N << 1];
void init() {
    scanf("%d%d", &n, &q);
    scanf("%s", s + 1);
    lct_init();
    build(1, n);
    cnt = 0, lst = ++cnt;
    for (int i = 1; i <= n; i++) extend(Tr(s[i]));
    for (int i = 1; i <= cnt; i++) b[l[i]]++;
    for (int i = 1; i <= n; i++) b[i] += b[i - 1];
    for (int i = 1; i <= cnt; i++) x[b[l[i]]--] = i;
    for (int i = 1; i <= cnt; ++i) {
        id[x[i]] = i;
        if (mrk[x[i]]) ver[l[x[i]]] = i;
    }
    for (int i = 1; i <= cnt; i++) {
        len[i] = l[x[i]];
        if (f[x[i]]) fa[i] = id[f[x[i]]];
    }
    int l, r;
    for (int i = 1; i <= q; i++) {
        scanf("%d%d", &l, &r);
        ask[i] = {l + 1, r + 1, i};
    }
    sort(ask + 1, ask + q + 1);
}
void solve() {
    int p = 1;
    for (int i = 1; i <= n; i++) {
        upd(1, n, 1, i, 1);
        access(ver[i], i);
        int pre = 0;
        for (int j = mcnt; j > 1; j--) {
            if (mp[j].first == 0) continue;
            if (mp[j].second != 0)
                upd(1, n, mp[j].second - mp[j].first + 1, mp[j].second - pre,
                    -1);
            pre = mp[j].first;
        }
        while (p <= q && ask[p].r == i) {
            ans[ask[p].id] = qry(1, n, ask[p].l, ask[p].r);
            p++;
        }
    }
    for (int i = 1; i <= q; i++) printf("%lldn", ans[i]);
}
int main() {
    init();
    solve();
    return 0;
}