题目描述
blablabla
样例
blablabla
算法1
(暴力枚举) $O(n^2)$
blablabla
时间复杂度
参考文献
C++ 代码
blablabla
算法2
(暴力枚举) $O(n^2)$
blablabla
时间复杂度
参考文献
C++ 代码
#include <iostream>
using namespace std;
const int INF = 0x5ffffff;
int N;
int G[110][110];
int main()
{
scanf("%d\n", &N);
for(int i = 1; i <= N; ++i){
for(int j = 1; j <= N; ++j)
if (i != j)
G[i][j] = INF;
}
int a, b;
for(int i = 0; i < N-1; ++i){
scanf("%d %d", &a, &b);
G[a][b] = 0;
}
for(int k = 1; k <= N; ++k){
for(int i = 1; i <= N; ++i){
for(int j = 1; j <= N; ++j){
if((G[i][k]+G[k][j]) < G[i][j])
G[i][j] = G[i][k]+G[k][j];
}
}
}
bool ok = true;
for(int i = 1; i <= N; ++i){
ok = true;
for(int j = 1; j <= N; ++j){
if(G[j][i] >= INF){
ok = false;
break;
}
}
if (ok){
cout << i << endl;
break;
}
}
if(!ok)
cout << -1 << endl;
return 0;
}