Ford&Bellman

#include <iostream>
#include <vector>
#include <algorithm>
#include <fstream>
#include <math.h>

int INF = 1000000;

int main()
{
    std::ifstream finp;
    finp.open("input.txt");
    int n = 0, a = 0, b = 0, x = 0;
    double c = 0;
    std::vector < std::pair<double, std::pair<int, int>> > e;
    std::vector<double> d;
    std::vector<double> p;
    finp >> n;
    d.resize(n, INF);
    p.resize(n, -1);
    for (int i = 0; i < n; i++)
    {
        for (int j = 0; j < n; j++)
        {
            if (i == j)
                continue;
            finp >> c;
            if(c > 0)
                e.push_back(std::make_pair(c, std::make_pair(i, j)));
        }
    }

    d[0] = 1;
    int fl = 0;

    for (int i = 0; i < n; i++)
    {
        for (int j = 0; j < e.size(); j++)
        {
            if (d[e[j].second.first] < INF)
            {
                if (i == n - 1 && d[e[j].second.second] > d[e[j].second.first] * e[j].first)
                {
                    fl = 1;
                    break;
                }
                d[e[j].second.second] = std::min(d[e[j].second.second], d[e[j].second.first] * e[j].first);
            }
        }
        if (fl)
            break;
    }

    if (!fl)
        std::cout << "No\n";
    else
        std::cout << "Yes\n";
    return 0;
}