题解

#include<list>
#include<iostream>
#include<algorithm>
using namespace std;

int main(){
    int n;
    cin>>n;
    list<int>node;
    for (int i=0;i<n;i++){
        int y;
        cin>>y;
        node.push_back(y);
    }
    int a,b;
    cin>>a>>b;
    auto it=find(node.begin(),node.end(),a);
    node.insert(++it,b);
    for (int j:node){
        cout<<j<<' ';
    }
}