POJ1007-DNA Sorting-ACM

DNA Sorting

Time Limit: 1000MS		Memory Limit: 10000K
Total Submissions: 83442		Accepted: 33584

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

重点，归并排序求逆序数

#include <stdio.h>
#include <malloc.h>
#include <string.h>
#define MAXN 256
char a[MAXN];
char c[MAXN];
int cnt=0;
void MergeSort(int l, int r){
    int mid, i, j, tmp;
    if( r > l+1 ){
        mid = (l+r)/2;
        MergeSort(l, mid);
        MergeSort(mid, r);
        tmp = l;
        for( i=l, j=mid; i < mid && j < r; ){
            if( a[i] > a[j] ){
                c[tmp++] = a[j++];
                cnt += mid-i; //
            }
            else c[tmp++] = a[i++];
        }
        if( j < r ) for( ; j < r; ++j ) c[tmp++] = a[j];
        else for( ; i < mid; ++i ) c[tmp++] = a[i];
        for ( i=l; i < r; ++i ) a[i] = c[i];
    }
}
int main(void){
    int n,m;
    scanf("%d%d",&n,&m);
    char ** strs = (char **)malloc(m*sizeof(char*));
    int * cnts = (int *)malloc(m*sizeof(int));
    int i;
    for(i = 0;i<m;i++){
        strs[i] = (char *)malloc((n+1)*sizeof(char));
        scanf("%s",strs[i]);
        //printf("%s
",strs[i]);
        cnt = 0;
        strcpy(a,strs[i]);
        //printf("%s
",a);
        MergeSort(0,n);
        //printf("%d
",cnt);
        cnts[i] = cnt;
    }
    
    for(i = 0;i<m-1;i++){
        int j,p=i;
        for(j = i+1;j<m;j++){
            if(cnts[p]>cnts[j]){
                p = j;
            }
        }
        if(p!=i){
            int tmp = cnts[p];
            cnts[p] = cnts[i];
            cnts[i] = tmp;
            char * str = strs[p];
            strs[p] = strs[i];
            strs[i] = str;
        }
    }
    for(i = 0;i<m;i++){
        printf("%s
",strs[i]);
        free(strs[i]);
    }
    free(strs);
    free(cnts);
    return 0;
}