37 lines
622 B
C++
37 lines
622 B
C++
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#include<bits/stdc++.h>
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using namespace std;
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const int MAX_A=100005;
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int to[MAX_A];
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int inDegree[MAX_A];
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int main() {
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int n;
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cin>>n;
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for (int i=1; i<=n; i++) {
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cin>>to[i];
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inDegree[to[i]]++;
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}
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queue<int> q;
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int cnt = 0;
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for (int i=1; i<=n; i++) {
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if (inDegree[i]==0) {
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q.push(i);
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cnt++;
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}
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}
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while (q.size()>0) {
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int t=q.front();
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q.pop();
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int v = to[t];
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inDegree[v]--;
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if (inDegree[v]==0) {
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q.push(v);
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cnt++;
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}
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}
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cout<<n-cnt<<endl;
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return 0;
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}
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