Submission #2949180

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Source Code Expand

#include <bits/stdc++.h>

using namespace std;

bitset <555> A[22][555], B[22][555], T;
bitset <555> D[555], E[555];
int n, m, ans;

int main()
{
	int i, j, k, f, a, b, t;
	
	scanf("%d%d", &n, &m);
	
	for(i=0; i<m; i++){
		scanf("%d%d", &a, &b);
		A[0][a][b] = 1;
		B[0][b][a] = 1;
	}
	
	for(i=1; i<=n; i++){
		D[i][i] = 1;
	}
	
	for(t=1; ; t++){
		for(i=1; i<=n; i++){
			for(j=1; j<=n; j++){
				T = A[t-1][i] & B[t-1][j];
				if(T != 0) A[t][i][j] = B[t][j][i] = 1;
			}
		}
		
		if((1 << t) >= n * n) break;
	}
	
	for(i=1; i<=n; i++){
		if(!A[t][1][i]){
			printf("-1\n");
			return 0;
		}
	}
	
	for(; t>=0; t--){
		for(i=1; i<=n; i++){
			T = D[1] & B[t][i];
			if(T == 0) break;
		}
		
		if(i <= n){
			for(i=1; i<=n; i++){
				for(j=1; j<=n; j++){
					T = D[i] & B[t][j];
					if(T != 0) E[i][j] = 1;
				}
			}
			
			for(i=1; i<=n; i++){
				D[i] = E[i];
				E[i] = 0;
			}
			
			ans += (1 << t);
		}
	}
	
	printf("%d\n", ans + 1);
	
	return 0;
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:13:23: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d", &n, &m);
                       ^
./Main.cpp:16:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d", &a, &b);
                        ^

Judge Result