Floyd Warshall's algorithm implementation in C++ (used to calculate all vertex pair distance) (better than dijkstra when E > V^3)

floyd_warshall.cpp

#include <bits/stdc++.h>

using namespace std;
typedef long long ll;

int main(){
    ios::sync_with_stdio(0);
    cout.tie(0);
    cin.tie(0);
    ll n, m, q;
    cin >> n >> m >> q;
    vector<vector<ll>> mat(n + 1, vector<ll>(n + 1, 1e16));
    for(ll i = 0; i < m; i++){
        ll a, b, w;
        cin >> a >> b >> w;
        mat[a][b] = mat[b][a] = min(mat[a][b], w);
    }
    for(ll k = 1; k <= n; k++){
        for(ll i = 1; i <= n; i++){
            for(ll j = i + 1; j <= n; j++){
                mat[i][j] = mat[j][i] = min(mat[i][j], mat[i][k] + mat[k][j]);
            }
        }
    }
    while (q--){
        ll a, b;
        cin >> a >> b;
        if(a == b) mat[a][b] = 0;
        if(mat[a][b] == 1e16) cout << -1 << '\n';
        else cout << mat[a][b] << '\n';
    }   
}