You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
38 lines
688 B
38 lines
688 B
#include <bits/stdc++.h>
|
|
|
|
using namespace std;
|
|
|
|
const int N = 1010, M = N << 2;
|
|
int e[M], h[N], idx, w[M], ne[M];
|
|
void add(int a, int b, int c = 0) {
|
|
e[idx] = b, ne[idx] = h[a], w[idx] = c, h[a] = idx++;
|
|
}
|
|
int n, m;
|
|
bool st[N];
|
|
int cnt;
|
|
void dfs(int u) {
|
|
st[u] = 1;
|
|
cnt++;
|
|
for (int i = h[u]; ~i; i = ne[i]) {
|
|
int v = e[i];
|
|
if (!st[v]) dfs(v);
|
|
}
|
|
}
|
|
|
|
int main() {
|
|
memset(h, -1, sizeof h);
|
|
cin >> n >> m;
|
|
for (int i = 1; i <= m; i++) {
|
|
int a, b;
|
|
cin >> a >> b;
|
|
add(a, b);
|
|
}
|
|
|
|
dfs(1);
|
|
|
|
if (cnt == n)
|
|
printf("Yes\n");
|
|
else
|
|
printf("No\n");
|
|
return 0;
|
|
} |