Educational Codeforces Round 9 C. The Smallest String Concatenation —— 贪心 + 字符串

题目链接：http://codeforces.com/problemset/problem/632/C

C. The Smallest String Concatenation

time limit per test

3 seconds

memory limit per test

256 megabytes

input

standard input

output

standard output

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

题解：

1.设有两个字符串a和b：求他们最小字典序的组合，那么只有两种情况 ： a+b 和 b+a，即取字典序小的那个。

2.字符串个数由两个推广到n个，那么即相当于在原基础上插入新的字符串，使得字典序最小。所以这是一个排序的过程。

代码如下：

 #include<bits/stdc++.h>
 using namespace std;
 typedef long long LL;
 const double eps = 1e-;
 const int INF = 2e9;
 const LL LNF = 9e18;
 const int mod = 1e9+;
 const int maxn = 5e4+;

 string s[maxn];
 int n;

 bool cmp(string a, string b)
 {
     return a+b<b+a;
 }

 int main()
 {
     cin>>n;
     for(int i = ; i<=n; i++)
         cin>>s[i];

     sort(s+,s++n,cmp);
     for(int i = ; i<=n; i++)
         cout<<s[i];
     cout<<endl;
     return ;
 }