数组就行

#include<bits/stdc++.h>
using namespace std;
int nn[1005];
int main(){
    int n; cin >> n;
    for(int i = 1;i <= n;i++) cin >> nn[i];
    int a,b; cin >> a >> b;
    for(int i = 1;i <= n;i++){
        if(nn[i] == a) cout << a << " " << b << " ";
        else cout << nn[i] << " ";
    }
    return 0;
}