HackerRank Gridland Metro problem solution

In this HackerRank Gridland Metro problem solution, The city of Gridland is represented as an n x m matrix where the rows are numbered from 1 to n and the columns are numbered from 1 to m.

Gridland has a network of train tracks that always run in straight horizontal lines along a row. In other words, the start and end points of a train track are (r,c1) and (r,c2), where r represents the row number, c1 represents the starting column, and c2 represents the ending column of the train track.

The mayor of Gridland is surveying the city to determine the number of locations where lampposts can be placed. A lamppost can be placed in any cell that is not occupied by a train track.

Given a map of Gridland and its k train tracks, find and print the number of cells where the mayor can place lampposts.

Note: A train track may overlap other train tracks within the same row.

HackerRank Gridland Metro problem solution in Python.

#!/usr/bin/env python3

def overlapped(c1, c2, g1, g2):
    if c1 == g2+1 or g1 == c2+1:
        return True
    elif g1 <= c1 <= g2 or g1 <= c2 <= g2:
        return True
    elif c1 <= g1 <= c2 or c1 <= g2 <= c2:
        return True

def update_gridland(r, c1, c2):
    if r not in gridland:
        gridland[r] = []
        gridland[r].append((c1,c2))
    else:
        trackadded = False
        for i in range(len(gridland[r])):
            if overlapped(c1, c2, gridland[r][i][0], gridland[r][i][1]):
                gridland[r][i] = (min(c1, gridland[r][i][0]), max(c2, gridland[r][i][1]))
                trackadded = True
                break
        if not trackadded:
            gridland[r].append((c1, c2))


n, m, k = list(map(int, input().strip().split()))
tracks = []
for i in range(k):
    tracks.append(tuple(map(int, input().strip().split())))
tracks = tuple(tracks)    

gridland = {}
for t in tracks:
    r, c1, c2 = t
    update_gridland(r, c1, c2)
    
used = 0
for row in gridland:
    for tracks in gridland[row]:
        used += abs(tracks[0]-tracks[1])+1
        
print(n*m - used)

Gridland Metro problem solution in Java.

import java.io.*;
import java.util.*;

public class Solution {

    static class MyRow {
        Long start = null;
        Long stop = null;
        
        long add(long start, long stop) {
            if(this.start == null || this.stop == null) {
                this.start = start;
                this.stop = stop;
                return this.stop - this.start + 1;
            }
            
            long newTracks = 0;
            if(start < this.start) {
                if(stop < this.start) {
                    //add hole
                    newTracks = stop - start + 1;
                } else {
                    long before = this.start - start;
                    if(stop <= this.stop) {
                        newTracks = before;
                    } else { //(stop > this.stop)
                        //both sides
                        newTracks = before + (stop - this.stop);
                    }
                }
                this.start = start;
            } else if(stop > this.stop) {
                if(start > this.stop) {
                    //add hole
                    newTracks = stop - start + 1;
                } else {
                    long after = stop - this.stop;
                    if(start >= this.start) {
                        newTracks = after;
                    } else {
                        //both sides (not reached)
                        newTracks = (start - this.start) + after;
                    }
                }
                this.stop = stop;
            } else {
                //take care of holes
            }
            return newTracks;
        }
    }
    
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        long N = in.nextLong();
        long M = in.nextLong();
        int K = in.nextInt();
        
        long lamppost = N*M;
        //System.out.println(N + ", " + M + ", " + K);
        Map<Long, MyRow> map = new HashMap<>();
        for(int i = 0; i < K; i++) {
            long row = in.nextLong();
            long start = in.nextLong();
            long stop = in.nextLong();
            
            MyRow theRow = map.get(row);
            if(theRow == null) {
                theRow = new MyRow();
            }
            long newTracks = theRow.add(start, stop);
            lamppost -= newTracks;
            map.put(row, theRow);
        }
        System.out.println(lamppost);
    }
}

Problem solution in C++.

#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;

class T {
    public:
    long r;
    long c1;
    long c2;
    long d;
    bool operator<( const T& t ) const {
        if (r != t.r) {
            return r < t.r;
        }
        
    	return c1 < t.c1;
    }
};

int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    long n, m;
    int k;
    
    scanf("%ld %ld %d", &n, &m, &k);
    vector<T> v(k);
    for(int i = 0; i < k; i++) {
        T t;
        scanf("%ld %ld %ld", &t.r, &t.c1, &t.c2);
        t.d = t.c2 - t.c1 + 1;
        v[i] = t;
    }
    
    sort(v.begin(), v.end());
    
    long non_empty_cells = 0;
    int pt = -1;
    for(int i = 0; i < k; i++) {
       // cout << v[i].r << ": " << v[i].c1 << " " << v[i].c2 << endl;
        if (v[pt].r != v[i].r || v[pt].c2 < v[i].c1) {
            non_empty_cells += v[i].d;
        }
        else {
            //cout << "merging" << endl;
            non_empty_cells -= v[pt].d;
            v[i].c1 = v[pt].c1;
            v[i].c2 = max(v[pt].c2, v[i].c2);
            v[i].d = v[i].c2 - v[i].c1 + 1;
            non_empty_cells += v[i].d;
        }
        
        pt = i;
    }
    
    long long total = n * m - non_empty_cells;
    cout << total << endl;
    return 0;
}

Problem solution in C.

#include <stdio.h>
#include <string.h>
#include <math.h>
#include <stdlib.h>

int min(int a, int b)
{
    if (a < b)
        return a;
    else
        return b;
}

int max(int a, int b)
{
    if (a > b)
        return a;
    else
        return b;
}

typedef struct bridge_ {
   unsigned long int row;
   unsigned long int start; 
   unsigned long int end;
   struct bridge_ *next;
} bridge; 

bridge *row[1001];

static int ctr = 0;


void insert (bridge **head, unsigned int start, unsigned int end, unsigned int row)
{
     bridge *prev = NULL;
     bridge *node = *head;
     bridge *new_node = (bridge *)malloc(sizeof(bridge));

     new_node->row = row;
     new_node->start = start;
     new_node->end = end;

    
     if (!node) {
         new_node->next = NULL;
         *head = new_node;
         return;
     }

     node = *head;
     if(!node) {
       *head = new_node;
    } else {
       while (node && start > node->start) {
          prev = node;
          node = node->next;
       }
       if (!prev) {
           new_node->next = *head;
           *head = new_node;
       } else {
           new_node->next = prev->next;
           prev->next = new_node;
       }
    }
}

unsigned long long int add_ranges(bridge *node)
{
   unsigned long long int range = 0;
   bridge *prev;
   int start, end;
    
   while (node != NULL) {
      prev = node;
      node = node->next; 
       
      end = prev->end; 
      start = prev->start;

      if (node != NULL && end >= node->start) {
          start = min(start, node->start);
          end = max(end, node->end);
          //printf("n%d %dn", start, end);
          while (node != NULL && end >= node->start) {
               end = max(end, node->end);
               node = node->next;
          }
      } 
      range += end - start + 1;
   }
   return range;
}

void print_row(bridge *head)
{
    bridge *tmp = head;
    printf("n");
    while(tmp != NULL) {
        printf("%ld %ld %ld-->", tmp->row, tmp->start, tmp->end);
        tmp = tmp->next;
    }
    printf("NULLn");
}

int find_entry(int r)
{
   int i;
   for (i = 0; i < ctr; i++) {
        if (!row[i])
            continue;
        if (row[i]->row == r)
            return i;
   }
   return -1;
}

int main() {
    unsigned long long n, m, t;
    unsigned long long i, r1, c1, c2;
    unsigned long long sum = 0;
    unsigned int idx;
    
    scanf("%lld%lld%lld", &n, &m, &t);

    sum = n * m;
    
    for (i = 1; i <= t; i++) 
         row[i] = NULL;

    for (i = 1; i <= t; i++) {
         scanf("%lld %lld %lld", &r1, &c1, &c2);
         idx = find_entry(r1);
         if (idx == -1) {
             idx = ctr;
             ctr++;
         }
         insert(&row[idx], c1, c2, r1);
    }    

    /* for (i = 0; i < ctr; i++)
         print_row(row[i]); */

    for (i = 0; i < ctr; i++) {
        sum -= add_ranges(row[i]);
    }

    printf("%lldn", sum);
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */    
    return 0;
}