[wrong question]

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#include<bits/stdc++.h>
using namespace std;
const int N = 2e6 + 10;
int n;
string A[N];
bool cmp(const string &a,const string &b){
    
    return a + b < b + a;
}
int main(){
    
    cin >> n;
    for(int i = 0;i < n;i++){
    
        cin >> A[i];
    }
    sort(A,A + n,cmp);
    for(auto it : A)
        printf("%s",it.c_str());
    return 0;
}

The official solution to this problem is to establish a trie, Reduce the time complexity to $O(n)$, But because of the platform environment , Can pass the card constant , use $O(lo{g}_{2}n)$ The complexity of the code passes .

For this question , Compare the relationship between two numbers , It only needs $a+b<b+a$, That is, think from the perspective of digital integrity , You can't find local rules on every character in a number .
That is, we need to have a holistic thinking .