HackerEarth Little Deepu and Array problem solution

In this HackerEarth Little Deepu and Array problem solution, Little Deepu loves positive things in life, positive girlfriends, positive marks. He’s, in general a lover of positive things, so for obvious reasons he loves an array which contains positive elements.

Anyway, Little Deepu also thinks that not every value in his so called positive array deserves to be valued so high, so he makes an operation called HIT which takes exactly one argument, i.e., HIT (X). When HIT (X) is called, it decreases the value of all the elements of the array by 1 which are greater than X.

Now, to test how positive can you stay in life, he performs M HIT operations, and after they have been done, Deepu wants you to print the final array.

#include<iostream>
#include<bits/stdc++.h>
using namespace std;
 //
#include<string.h>
#include<math.h> 
 

#define MAX 100005
#define inf 0x7fffffff

int N; 
int arr[MAX];
int tree[4*MAX];
int lazy[4*MAX];
 
/**
 * Build and init tree
 */
void build_tree(int node, int a, int b) {
    if(a > b) return; 
    
    if(a == b) { 
            tree[node] = arr[a]; 
        return;
    }
    
    build_tree(node*2, a, (a+b)/2); 
    build_tree(node*2+1, 1+(a+b)/2, b); 
    
    tree[node] = min(tree[node*2], tree[node*2+1]);
}
 
/**
 * Increment elements within range [i, j] with value value
 */
void update_tree(int node, int a, int b, int i, int j, int x, int value) {

   

     if(a > b || a > j || b < i) // Current segment is not within range [i, j]
        return;

    if(lazy[node] != 0) { // This node needs to be updated
        tree[node] += lazy[node]; // Update it
 
        if(a != b) {
            lazy[node*2] += lazy[node]; // Mark child as lazy
        lazy[node*2+1] += lazy[node]; // Mark child as lazy
        }
 
    lazy[node] = 0; // Reset it
    }
  

    
    if(tree[node] > x) { // Segment is fully within range
    tree[node] += value;
        if(a != b) { // Not leaf node
                lazy[node*2] += value;
                lazy[node*2+1] += value;
        }
      return;
  }
  
  if(a == b) return;

    update_tree(node*2, a, (a+b)/2, i, j,x, value); // Updating left child
    update_tree(1+node*2, 1+(a+b)/2, b, i, j,x, value); // Updating right child
 
    tree[node] = min(tree[node*2], tree[node*2+1]); // Updating root with max value
}

 
/**
 * Query tree to get max element value within range [i, j]
 */
int query_tree(int node, int a, int b, int i, int j) {
    
    if(a > b || a > j || b < i) return inf;
 
    if(lazy[node] != 0) { 
        tree[node] += lazy[node];
 
        if(a != b) {
            lazy[node*2] += lazy[node]; 
            lazy[node*2+1] += lazy[node]; 
        }
 
        lazy[node] = 0; 
    }
 
    if(a >= i && b <= j) 
        return tree[node];
 
    int q1 = query_tree(node*2, a, (a+b)/2, i, j); 
    int q2 = query_tree(1+node*2, 1+(a+b)/2, b, i, j); 
    int res = min(q1, q2); 
    
    return res;
}
 
int main() {
    cin >> N;
    assert(N < 1000001);
    vector<pair<int,int> > ds;
    for(int i=0;i<N;i++){
        int a;
        cin >> a;
        assert(a < 1000000000);
        ds.push_back(make_pair(a,i+1));
    }
    sort(ds.begin(),ds.end());
    for(int i=0;i<N;i++){
        arr[i] = ds[i].first;
    }
    build_tree(1, 0, N-1);
    memset(lazy, 0, sizeof lazy);
    int Q;
    cin >> Q;
    assert(Q <= 20000);
    while(Q--){
        int x;
        cin >> x;
        assert(x <= 1000000000);
        update_tree(1, 0, N-1 , 0 , N-1, x, -1);
    }
    for(int i=0;i<N;i++){
        ds[i].first = query_tree(1, 0, N-1, i, i);
        swap(ds[i].first, ds[i].second);
    }
    sort(ds.begin(),ds.end());
    for(int i=0;i<N;i++){
        cout << ds[i].second << " ";
    }
    cout << endl;
}