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| #include <bits/stdc++.h>
#define ios ios::sync_with_stdio(0),cin.tie(0)
#define lld long long
#define N 1000
using namespace std;
int n,m;
bool visit[N];
vector<int>edge[N];
void dfs(int cur){
visit[cur] = 1;
for(auto i:edge[cur]){
if(visit[i])continue;
dfs(i);
}
}
void solve(){
memset(visit,0,sizeof(visit));
for(int i=0;i<=n+100;i++)edge[i].clear();
for(int i=0;i<m;i++){
int x,y;cin>>x>>y;
edge[x].push_back(y);
}
int from,to;cin>>from>>to;
dfs(from);
if(visit[to])cout<<"Yes"<<endl;
else cout<<"No"<<endl;
}
signed main(){
while(cin>>n>>m){
solve();
}
}
|