L - The Smallest String Concatenation

CodeForces - 632C

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

题意：对给定字符串排序，使排序后的字典序最小

解法：自定义sort函数的比较函数cmp，对字符串进行排序，然后依次输出。比较函数即比较两个字符串谁放在前面字典序小，所以比较a+b和b+a

代码：

#include<iostream>
#include<string>
#include<cstring>
#include<algorithm>
using namespace std;
string n[50005];
bool cmp(string a,string b)
{
    return a+b<b+a;
}
int main()
{
    int num;
    cin>>num;
    for(int i=0;i<num;i++)
        cin>>n[i];
    sort(n,n+num,cmp);
    for(int i=0;i<num;i++)
        cout<<n[i];
    return 0;
}