Submission #197520

#	Time	Username	Problem	Language	Result	Execution time	Memory
197520		handlename	Forensic (NOI12_forensic)	C++17	25 / 25	5 ms	1404 KiB

forensic

#include <bits/stdc++.h>
using namespace std;
int n,arr[20001];
bool vis[20001],vis2[20001];
int maxi[20001];
vector<int> brr;
bool loop;
void dfs(int cur){
    if (cur==-1) return;
    if (vis[cur]){
        loop=true;
        return;
    }
    vis[cur]=true;
    maxi[cur]=0;
    brr.push_back(cur);
    dfs(arr[cur]);
}
int dfs2(int cur){
    if (cur==-1) return 0;
    if ((vis[cur] && loop) || cur==0) return -1e9;
    if (maxi[cur]!=-1) return maxi[cur];
    if (vis2[cur]) return -1e9;
    vis2[cur]=true;
    maxi[cur]=dfs2(arr[cur])+1;
    return maxi[cur];
}
int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cin>>n;
    for (int i=0;i<n;i++) cin>>arr[i];
    if (arr[0]==0){
        cout<<1;
        return 0;
    }
    memset(maxi,-1,sizeof(maxi));
    dfs(0);
    int ans=0;
    for (int i=0;i<n;i++){
        if (!vis[i]){
            ans=max(ans,dfs2(i));
        }
    }
    cout<<brr.size()+ans;
}

• Subtask 1: 5 / 5
• Subtask 2: 5 / 5
• Subtask 3: 5 / 5
• Subtask 4: 10 / 10