Monotonic

#include <bits/stdc++.h>
 
#define ll long long
#define lll __int128
#define pii pair<int, int>
#define M 1000000007
#define N 101
#define PB push_back
#define F first
#define S second
using namespace std;
 
int e[20][20];
 
int solve() {
	int n, m;
	cin>>n>>m;
	pii p[m];
	
	for (int i = 0; i < n; i++) {
		for (int j = 0; j < n; j++) {
			e[i][j] = n * n;
		}
		e[i][i] = 0;
	}
	
	for (int i = 0; i < m; i++) {
		cin>>p[i].F>>p[i].S;
		p[i].F--;
		p[i].S--;
		e[p[i].F][p[i].S] = 1;
	}
	int ans = 0;
	
	for (int k = 0; k < n; k++) {
		for (int i = 0; i < n; i++) {
			for (int j = 0; j < n; j++) {
				e[i][j] = min(e[i][j], e[i][k] + e[k][j]);
			}
		}
	}
	for (int i = 0; i < n; i++) {
		for (int j = i; j < n; j++) {
			if (e[i][j] == n * n) return -1;
			ans = max(ans, e[i][j]);
		}
	}
	return ans;
}
 
int main () {
	srand(time(0));
	cin.sync_with_stdio(false);
	cin.tie(0);
	ll t; cin >> t;
	while(t--) cout << solve() << "\n";
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: WRONG ANSWER

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: WRONG ANSWER

Test 9

Verdict: WRONG ANSWER

Test 10

Verdict: WRONG ANSWER