HackerRank

Typical Floyd-Walshall Algorithm.

#include <cmath>
#include <cstdio>
#include <vector>
#include <string>
#include <iostream>
#include <algorithm>
#include <queue>
#include <unordered_map>
#include <unordered_set>
using namespace std;

const long DIST_MAX = std::numeric_limits<long>::max();

int main() 
{
        const int INF = std::numeric_limits<int>::max();
        
        //    Get input
        int n, m; cin >> n >> m;
        vector<vector<int>> dist(n, vector<int>(n, INF));
        int mm = m;
        while (mm--){
            int x, y, r;
            cin >> x >> y >> r;
            dist[x - 1][y - 1] = r;
        }
        for (int i = 0; i < n; i++)
            dist[i][i] = 0;

        //    Floyd-Walshall
        for (int v = 0; v < n; v ++)
        for (int f = 0; f < n; f++)
        for (int t = 0; t < n; t++)
        {
            if (f == t) continue;

            int fv = dist[f][v];
            int vt = dist[v][t];            
            if (fv != INF && vt != INF)
            {
                if (dist[f][t] > (fv + vt))
                    dist[f][t] = fv + vt;
            }
        }

        //    Queries
        int q; cin >> q;
        while (q--)
        {
            int a, b; cin >> a >> b;
            int ret = dist[a - 1][b - 1];
            cout << (ret == INF ? -1 : ret) << endl;
        }
    
    return 0;
}