CodeForces 630C

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.

Examples
input
4
abba
abacaba
bcd
er
output
abacabaabbabcder
input
5
x
xx
xxa
xxaa
xxaaa
output
xxaaaxxaaxxaxxx
input
3
c
cb
cba
output
cbacbc

—————————————————————————分割线。这题就是要你把n的字符串拼起来。然后让字典序最小。就是就是排个序的问题。两个字符串连起来，要么就是a+b，或者是b+a.我们要让n的字符串连起来最小，那么每次连接都选小就可以啦。
cmp函数可以这样写
bool cmp(string a,string b)
{
return a+b

#include<stdio.h>
#include<string.h>
#include<iostream>
#include<algorithm>
#include<map>
#include<set>
#include<vector>
#include<string>
using namespace std;
const int N=1000000;
string  str[N];
bool cmp(string a,string b){
    return (a+b<b+a);
}
int main()
{
    int n;
    scanf("%d",&n);
    for(int i=0;i<n;i++)
    {
        cin>>str[i];
    }
    sort(str,str+n,cmp);
    for(int i=0;i<n;i++)
    {
        cout<<str[i];
    }
    cout<<"
";
    return 0;
}