61 lines
1.2 KiB
C++
61 lines
1.2 KiB
C++
#include <iostream>
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#include <istream>
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#include <ranges>
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#include <queue>
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#include <limits>
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#include <algorithm>
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using std::cin,std::cout;
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constexpr const auto range = std::ranges::views::iota;
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const int MAX_N = 2e5+5;
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int n;
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int next[MAX_N];
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int in_degree[MAX_N];
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std::queue<int> q;
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bool vis[MAX_N];
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int ans {std::numeric_limits<int>::max()};
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int main(){
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std::iostream::sync_with_stdio(false),cin.tie(nullptr),cout.tie(0);
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cin>>n;
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for(const int i:range(1,n+1)){
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cin>>next[i];
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in_degree[next[i]]++;
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}
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const auto push_vis = [](const int n){
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q.push(n);
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vis[n]=true;
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};
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for(const int i:range(1,n+1)){
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if(in_degree[i]==0){
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push_vis(i);
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}
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}
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while(q.empty()==false){
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int front = q.front();
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q.pop();
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in_degree[next[front]]--;
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if(in_degree[next[front]]==0){
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push_vis(next[front]);
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}
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}
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for(int i:range(1,n+1)){
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if(vis[i])continue;
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const int start {i};
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int now {start};
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int ring_size {0};
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do{
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vis[now]=true;
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ring_size++;
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now = next[now];
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}while(now!=start);
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ans = std::min(ans,ring_size);
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}
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cout<<ans<<"\n";
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}
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