Acwing 379. hide and seek problem solution (minimum path non repeating point coverage)

AcWing 379. hide-and-seek

Big guy problem solving original address

#include<bits/stdc++.h>

using namespace std;

const int N = 210, M = 61000;

bool d[N][N], st[N];
int n, m;
int match[N];

bool find(int u){
    
	for(int i = 1; i <= n; i ++ ){
      // Traverse all points to see which can be connected  
		if(d[u][i] && !st[i]){
    
			st[i] = true;
			int t = match[i];
			if(t == 0 || find(t)){
    
				match[i] = u;
				return true;
			}
		}
	}
	return false;
}

int main()
{
    
	cin>>n>>m;
	for(int i = 0; i < m; i ++ ){
    
		int a, b;
		cin>>a>>b;
		d[a][b] = true;
	}
	
	for(int k = 1; k <= n; k ++ ){
    
		for(int i = 1; i <= n; i ++ ){
    
			for(int j = 1; j <= n; j ++ ){
    
				d[i][j] |= d[i][k] & d[k][j];  // Finding transitive closure , It is to connect a point on a road with all the points that can be connected behind  
			}
		}
	}
	
	int res = 0;
	for(int i = 1; i <= n; i ++ ){
    
		memset(st, 0, sizeof st);
		if(find(i)) res ++ ;
	}
	
	cout<<n - res <<endl;
	return 0;
}