再遇结构体- A - DNA Sorting

A - DNA Sorting

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'' toleast 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

这道题本来暴力循环排序就可以了，结果智障的小菜鸡数组开小了，一直Runtime Error 
误以为循环超时，又去博客看了看大牛的解法，再次拾起了结构体，
顺带了解了一波c++的sort和stable_sort;前前后后改了两个小时
最后发现是数组开小了，真是被自己蠢笑了

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <string>
#include<stdlib.h>
using namespace std;
struct DNA
{
	string dna;
	int len;
};
bool compare(DNA x,DNA y)
{
	return x.len<y.len;
}
int main()
{
	struct DNA a[102];
	int i,j,n,m;
	scanf("%d%d",&n,&m);
	for(i=0;i<m;i++)
	{
		cin>>a[i].dna;
		a[i].len=0;
		for(j=0;j<=n-2;j++)
		{
			for(int k=j+1;k<=n-1;k++)
			{
				if(a[i].dna[j]>a[i].dna[k])
				{
					a[i].len++;
				}
			}
		}
	}
	stable_sort(a,a+m,compare);
	for(i=0;i<m;i++)
	{
		cout<<a[i].dna<<endl;
	}
	return 0;
}