The Smallest String Concatenation CodeForces

You’re given a list of n strings a1, a2, …, an. You’d like to concatenate them together in some order such that the resulting string would be lexicographically smallest.

Given the list of strings, output the lexicographically smallest concatenation.

Input
The first line contains integer n — the number of strings (1 ≤ n ≤ 5·104).

Each of the next n lines contains one string ai (1 ≤ |ai| ≤ 50) consisting of only lowercase English letters. The sum of string lengths will not exceed 5·104.

Output
Print the only string a — the lexicographically smallest string concatenation.

Example
Input
4
abba
abacaba
bcd
er
Output
abacabaabbabcder
Input
5
x
xx
xxa
xxaa
xxaaa
Output
xxaaaxxaaxxaxxx
Input
3
c
cb
cba
Output
cbacbc

题目很好理解，关键在于怎么排序

#include<stdio.h>#include<string>#include<iostream>#include<algorithm>using namespace std;string a[50010];int n;int cmp(string a,string b){    return a+b < b+a;  // 想到这样排序就好了。。。}int main(){    scanf("%d",&n);    for(int i=0;i<n;i++)        cin >> a[i];    sort(a,a+n,cmp);    for(int i=0;i<n;i++)        cout << a[i];    return 0;   }