正经题解，字符串插入，不用substr

正经题解

#include <bits/stdc++.h>
using namespace std;
int main() {
    int n;
    cin>>n;
    while (n--) {
        string a;
        cin>>a;
        int len = a.size();
        bool found = false;
        for(int k = 2;k <= len - 2;k++){
            string x1 = "", y1 = "";
            for(int i = 0;i < k;i++){
                x1 += a[i];
                y1 = a[i] + y1;
            }
            string x2 = "", y2 = "";
            for(int i = k;i < len;i++){
                x2 += a[i];
                y2 = a[i] + y2;
            }
            if(x1 == y1 && x2 == y2){
                found = true;
                break;
            }
        }
        if(found){
            cout << "Yes" << endl;
        }else{
            cout << "No" << endl;
        }
    }
    return 0;
}