Constraints

Time Limit: 1 secs, Memory Limit: 32 MB

Description

Dr lee cuts a string S into N pieces,s[1],…,s[N].   

Now, Dr lee gives you these N sub-strings: s[1],…s[N]. There might be several possibilities that the string S could be. For example, if Dr. lee gives you three sub-strings {“a”,“ab”,”ac”}, the string S could be “aabac”,”aacab”,”abaac”,…   

Your task is to output the lexicographically smallest S. 

Input

        The first line of the input is a positive integer T. T is the number of the test cases followed.   

The first line of each test case is a positive integer N (1 <=N<= 8 ) which represents the number of sub-strings. After that, N lines followed. The i-th line is the i-th sub-string s[i]. Assume that the length of each sub-string is positive and less than 100. 

Output

The output of each test is the lexicographically smallest S. No redundant spaces are needed. 

Sample Input

1
3
a
ab
ac

Sample Output

aabac

Problem Source

ZSUACM Team Member

这道题的思路比较简单，题目每次给出n个字符串，然后要求输出用这n个字符串组合成的字典序最小的字符串，字符串需全部使用且不能重复使用。

首先我们要知道如何判断组成字典序最小的组合顺序，由字符串a和b，如果a+b小于b+a，那么我们就选择b+a组合，反之则选择a+b组合，基于这样一种判断，我们可以直接定义一个cmp对所有字符串进行sort排序即可；

在cmp(const string &x1,const string &x2)中，我们只需返回x1+x2<x2+x1即可，那么我们最终得到的排序按顺序输出，就是题目所要求的字典序最小的字符串。

代码如下：

#include <iostream>
#include <algorithm>
using namespace std;
string s[16];
bool cmp(const string &x1,const string &x2)
{  
    return x1+x2<x2+x1;  
}
int main()
{
	int t;
	cin>>t;
	while(t--)
	{
		int n;
		cin>>n;
		for(int i=0;i<n;i++)
		{
			cin>>s[i];
		}
		sort(s,s+n,cmp);
		for(int i=0;i<n;i++)
		{
			cout<<s[i];
		}
		cout<<endl;
	}
	return 0;
}

Sicily 1198 Substring

原文：http://www.cnblogs.com/RiTianBigBrother/p/5309363.html