UVA 10905 Children's Game (贪心)

Children's Game

Problem Description

There are lots of number games for children. These games are pretty easy to play but not so easy to make. We will discuss about an interesting game here. Each player will be given N positive integer. (S)He can make a big integer by appending those integers after one another. Such as if there are 4 integers as 123, 124, 56, 90 then the following integers can be made – 1231245690, 1241235690, 5612312490, 9012312456, 9056124123 etc. In fact 24 such integers can be made. But one thing is sure that 9056124123 is the largest possible integer which can be made.

Input

Each input starts with a positive integer N (≤ 50). In next lines there are N positive integers. Input is terminated by N = 0, which should not be processed.

Output

For each input set, you have to print the largest possible integer which can be made by appending all the N integers.

Sample Input

4
123 124 56 90
5
123 124 56 90 9
5
9 9 9 9 9
0

Sample Output

9056124123
99056124123
99999

题目链接：https://vjudge.net/problem/UVA-10905

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基本思路就是：按照最优顺序排序
这里的最优顺序就是尽可能的保证：权高的位获得数字大的数
实现：当时我想到的只是使用 string的重载运算符 > 来排序。
string s1>string s2 : 根据字典序比较
一般的 ：123 124 56 90
字典序排序后 ：90 56 124 123 正确
但例如 ：9421 942 234 123
字典序排序后 ：9421 942 234 123 错误
     正确的 ：942 9421 234 123 正确
排序规则：s1+s2>s2+s1 ps:(bool cmp() 规定的是一个小于的规则)
一般的 942 4234
942 4234>4234 942
之前的 9421 942
942 9421>9421 942

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AC代码如下：

#include <iostream>
#include <string>
#include <algorithm>
using namespace std;
const int MAXN=52;
string ss[MAXN];
bool cmp(string s1,string s2)
{//规定一个小于的规则 true：s[1]，s[2] 代入后为真。
    return s1+s2>s2+s1;
}
int main()
{
    int n;
    while(cin>>n&&n)
    {
        for(int i=0;i<n;i++)
            cin>>ss[i];
        sort(ss,ss+n,cmp);
        for(int i=0;i<n;i++)
            cout<<ss[i];
        cout<<endl;
    }
    return 0;
}

2017-03-06 13:27:42