Time Limit: 1000MS   Memory Limit: 10000K
Total Submissions: 79776   Accepted: 32061

Description

One measure of ``unsortedness'' in a sequence is the number of pairs of entries that are out of order with respect to each other. For instance, in the letter sequence ``DAABEC'', this measure is 5, since D is greater than four letters to its right and E is greater than one letter to its right. This measure is called the number of inversions in the sequence. The sequence ``AACEDGG'' has only one inversion (E and D)---it is nearly sorted---while the sequence ``ZWQM'' has 6 inversions (it is as unsorted as can be---exactly the reverse of sorted). 

You are responsible for cataloguing a sequence of DNA strings (sequences containing only the four letters A, C, G, and T). However, you want to catalog them, not in alphabetical order, but rather in order of ``sortedness'', from ``most sorted'' to ``least sorted''. All the strings are of the same length. 

Input

The first line contains two integers: a positive integer n (0 < n <= 50) giving the length of the strings; and a positive integer m (0 < m <= 100) giving the number of strings. These are followed by m lines, each containing a string of length n.

Output

Output the list of input strings, arranged from ``most sorted'' to ``least sorted''. Since two strings can be equally sorted, then output them according to the orginal order.

Sample Input

10 6
AACATGAAGG
TTTTGGCCAA
TTTGGCCAAA
GATCAGATTT
CCCGGGGGGA
ATCGATGCAT

Sample Output

CCCGGGGGGA
AACATGAAGG
GATCAGATTT
ATCGATGCAT
TTTTGGCCAA
TTTGGCCAAA

Source

East Central North America 1998
题目应该是挺简单的，所以还是比较适合我这种新手的。但是，因为在循环中一个小细节的错误，导致我花了挺长时间来找这个bug的。但是，以后也有了一点经验。先贴一下原来的有bug的代码吧 
 1 #include<iostream>
 2 #include<string>
 3 using namespace std;
 4 using std::string;
 5 const int NUM = 100;
 6 const int MAX = 1000;
 7 int main()
 8 {
 9     string str[NUM];//dna数组
10     int measure[NUM];//混乱度数组
11     int length, numbers;
12     cin >> length >> numbers;
13     for (int i = 0; i != numbers; ++i){
14         cin >> str[i];
15         measure[i] = 0;
16         for (int j = 0; j != length; ++j){
17             for (int k = j + 1; k != length; ++k){
18                 if (str[i][j] > str[i][k])
19                     ++measure[i];
20             }
21         }
22     }
23     for (int count = 0; count != numbers; ++count){
24         int temp = measure[0];
25         int pos = 0;
26         for (int index = 1; index != numbers; ++index){
27             if (temp > measure[index]){
28                 temp = measure[index];
29                 ++pos;//记录混乱度最小的dna的下标
30             }
31         }
32         measure[pos] = MAX;//将已找到混乱度最小的dna的混乱度该为最大，方便第n次循环找第n大的混乱度
33         cout << str[pos] << endl;
34     }
35     system("pause");
36     return 0;
37 }

不知道下次能不能直接找到这个bug。这个bug给我的经验是，在循环中的变量很有可能会出错，所以要么编写的时候深思熟虑，要么debug的时候直接将循环演示一遍，那就一目了然了。

1 for (int index = 1; index != numbers; ++index){
2             if (temp > measure[index]){
3                 temp = measure[index];
4                 pos = index;//记录混乱度最小的dna的下标
5             }
6     }

这是正确的代码。记录这题的另一个目的是，以后若是完整的学习了算法和数据结构，可以试试能不能将它优化一下。

刚刚查了一下别人的源码，发现有一种qsort（），明天要好好学习一下！

keep coding!