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merge_sort.c
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merge_sort.c
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/*
* merge_sort.c
*
* Created on: 2012-4-27
* Author: hujin
*/
#include <stdio.h>
#include <malloc.h>
#include <string.h>
#define swap(a, b) \
{ \
char tmp;\
tmp = a;\
a = b;\
b = tmp;\
}
void merge(char * arr, int start,int mid, int end) {
if(end - start == 1) {
if (arr[start] > arr[end]) {
swap(arr[start], arr[end]);
}
}else {
int len = end - start + 1; //NOTICE: The len should be end - start + 1 .
char * tmp = malloc(sizeof(char) * len);
int i = start, j = mid + 1, k = 0;
while(i <= mid && j <= end) {
if(arr[i] < arr[j]) {
tmp[k++] = arr[i++];
}else{
tmp[k++] = arr[j++];
}
}
while(i <= mid) {
tmp[k++] = arr[i++];
}
while(j <= end) {
tmp[k++] = arr[j++];
}
for(k = start, i=0; i < len; i ++, k ++) {
arr[k] = tmp[i];
}
free(tmp);
}
}
void _merge_sort(char * arr, int start, int end) {
if(start < end) {
int mid = start + ((end - start) >> 1);
_merge_sort(arr, start, mid);
_merge_sort(arr, mid + 1, end);
merge(arr, start,mid,end);
}
}
void merge_sort(char * arr, int len) {
if(len < 0) {
len = strlen(arr);
}
_merge_sort(arr, 0 , len - 1);
}