Floyd

// First task

#include <iostream>
#include <fstream>
#include <vector>
#include <string>
using namespace std;

int main() {

    std::ifstream fin("input.txt");
    std::ofstream fout("output.txt");

    int n;
    fin >> n;
    vector<vector<int>> m(n, vector<int> (n));

    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < n; ++j) {
            fin >> m[i][j];
        }
    }

    for (int k = 0; k < n; ++k) {
        for (int i = 0; i < n; ++i) {
            for (int j = 0; j < n; ++j) {

                m[i][j] = min(m[i][j], m[i][k] + m[k][j]);

            }
        }
    }

    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < n; ++j) {
            fout << m[i][j] << " ";
        }
        fout << endl;
    }
    return 0;

}

// Second task

#include <iostream>
#include <fstream>
#include <vector>
#include <string>
using namespace std;

int main() {

    std::ifstream fin("input.txt");
    std::ofstream fout("output.txt");

    int n;
    fin >> n;
    vector<vector<int>> m(n, vector<int>(n));

    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < n; ++j) {
            fin >> m[i][j];
        }
    }

    int max = -1;

    for (int k = 0; k < n; ++k) {
        for (int i = 0; i < n; ++i) {
            for (int j = 0; j < n; ++j) {

                if (m[i][k] != -1 && m[k][j] != -1)
                    if (m[i][j] == -1) {
                        m[i][j] = m[i][k] + m[k][j];
                    }
                    else {
                        m[i][j] = min(m[i][j], m[i][k] + m[k][j]);
                    }

            }
        }
    }

    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < n; ++j) {

            if (m[i][j] > max)
                max = m[i][j];
        }
    }

    fout << max;
    return 0;

}