CodeForces-632C-The Smallest String Concatenation

C - The Smallest String Concatenation
Time Limit:3000MS Memory Limit:262144KB 64bit IO Format:%I64d & %I64u
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Practice

CodeForces 632C
Description
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.

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

个人计分赛第三场。
就做过的四道题来看，考的都是英语六级阅读理解，对此真的很无语。

借用强大的string类，直接sort排序，cmp函数内定义好排序规则。
看题半小时，代码五分钟，真是醉了
代码

#include <iostream>
#include<algorithm>
#include<stdio.h>
#include<math.h>
#include<string>
#include<string.h>
using namespace std;
int cmp(string str1,string str2)
{
    return str1+str2<str2+str1;
}
int main()
{
    int n;
    while(scanf("%d",&n)!=EOF)
    {
        string str[50005];
        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];
        printf("\n");
    }
    return 0;
}

以前一直用string类，还没好好总结过用法，有时间总结一下吧