归并排序 C语言实现

1. 归并排序（排序的方法一种，速度比选择排序、插入排序等快很多）适合较多数据排序 

2. 归并排序思想（拆分、合并）

2.1 拆分

2.2 合并 

2.2 合并详解

3. c语言代码实现 

#include<stdio.h>
#define ArrLen 20
void printList(int arr[], int len) {
	int i;
	for (i = 0; i < len; i++) {
		printf("%d\t", arr[i]);
	}
}
void merge(int arr[], int start, int mid, int end) {
	int result[ArrLen];
	int k = 0;
	int i = start;
	int j = mid + 1;
	while (i <= mid && j <= end) {
		if (arr[i] < arr[j]){
			result[k++] = arr[i++];
        }
		else{
			result[k++] = arr[j++];
        }
	}
	if (i == mid + 1) {
		while(j <= end)
			result[k++] = arr[j++];
	}
	if (j == end + 1) {
		while (i <= mid)
			result[k++] = arr[i++];
	}
	for (j = 0, i = start ; j < k; i++, j++) {
		arr[i] = result[j];
	}
}

void mergeSort(int arr[], int start, int end) {
	if (start >= end)
		return;
	int mid = ( start + end ) / 2;
	mergeSort(arr, start, mid);
	mergeSort(arr, mid + 1, end);
	merge(arr, start, mid, end);
}

int main()
{
	int arr[] = {4, 7, 6, 5, 2, 1, 8, 2, 9, 1};
	mergeSort(arr, 0, 9);
	printList(arr, 10);
	system("pause");
	return 0;
}