Submission #39607983

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Source Code Expand

/**
 * @file template.cpp
 * @author Emanual20(Emanual20@foxmail.com)
 * @brief For Codeforces, Atcoder or some other OJs else
 * @version 0.1
 * @date 2023-3-11
 * 
 * @copyright Copyright (c) 2022
 * 
 */
#pragma GCC optimize(2)
#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;

const int maxn = 2e5 + 10;
const int inf = 0x3f3f3f3f;
int n, a[maxn];
set<int> st;

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0), cout.tie(0);

    cin >> n;
    for (int i = 1; i <= n; i++){
        cin >> a[i], st.insert(i);
    }
    for (int i = 1; i <= n; i++){
        if(st.count(i) == 1)
            st.erase(a[i]);
    }
    cout << st.size() << endl;
    for (auto &it : st){
        cout << it << " ";
    }
    return 0;
}

Submission Info

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