歸併排序

package com.sort;

public class MergeSort {
	public static void main(String[] args) {
		int[] a=new int[]{-6,5,4,3,-2,1};
		mergeSort(a,0,a.length-1);
		for(int array:a){
			System.out.println(array);
		}
	}
	
	public static void mergeSort(int[]a ,int start, int end){
		if(start >= end){
			return;
		}
		int mid = (start+end)/2;
		mergeSort(a, start, mid);
		mergeSort(a, mid+1, end);
		merge(a, start, mid, end);
	}

	private static void merge(int[] a, int first, int mid, int last) {
		int[] temp = new int[(last-first+1)];
	    int i = first;int j = mid + 1;  
	    int m = mid;int n = last;  
	    int k = 0;  
	    while (i <= m && j <= n)  
	    {  
	        if (a[i] <= a[j])  
	            temp[k++] = a[i++];  
	        else  
	            temp[k++] = a[j++];  
	    }  
	    while (i <= m)  
	        temp[k++] = a[i++];  
	      
	    while (j <= n)  
	        temp[k++] = a[j++];  
	    for (i = 0; i < k; i++)  
	        a[first + i] = temp[i];  
	}
}