【拓扑排序topsort】——启动！！！

B3644 【模板】拓扑排序 / 家谱树

#include<bits/stdc++.h>
#define int long long
#define fi first
#define se second
#define pb push_back
#define PII pair<int,int >
#define IOS ios::sync_with_stdio(false),cin.tie(0),cout.tie(0)
using namespace std;
const int N = 1e6+5;
int n,m;
int in[N];
vector<int> v[N];
void topsort()
{vector<int> e;queue<int> q;for(int i=1;i<=n;i++) if(in[i]==0) q.push(i);while(q.size()){auto now = q.front();e.pb(now);q.pop();for(auto spot : v[now]){if(--in[spot]==0) q.push(spot);}}for(auto t:e) cout<<t<<" ";
}
signed main()
{IOS;cin>>n;for(int i=1;i<=n;i++){int x;while(cin>>x&&x!=0){v[i].pb(x);in[x]++;}}topsort();
}

P2712 摄像头

#include<bits/stdc++.h>
#define int long long
#define fi first
#define se second
#define pb push_back
#define PII pair<int,int >
#define IOS ios::sync_with_stdio(false),cin.tie(0),cout.tie(0)
using namespace std;
const int N = 1e6+5;
int n,m;
vector<int> v[N];
set<int> s;
int in[N];
int cnt=0;
void topsort()
{queue<int> q;for(int i=1;i<=510;i++) if(in[i]==0&&s.count(i)) {q.push(i);//没有摄像头看着并且该位置有摄像头} while(q.size()){auto now = q.front();cnt++;q.pop();for(auto spot:v[now]){if(--in[spot]==0&&s.count(spot))//这个摄像头照着的地方可能没有摄像头 {q.push(spot);} }}
}
signed main()
{IOS;cin>>n;for(int i=1;i<=n;i++){int x,m;cin>>x>>m;s.insert(x);while(m--){int y;cin>>y;v[x].pb(y);in[y]++;}}topsort();	if(cnt!=n) cout<<n-cnt;else cout<<"YES";	
}