MergeSort

MergeSort: ref.1

import java.util.*;

public class MergeSort{

	public static void merge(int[] a, int low, int mid, int high) {
		int[] tmp = new int[high - low + 1];
		int i = low;// 左指针
		int j = mid + 1;// 右指针
		int k = 0;
		// 把较小的数先移到新数组中
		while (i <= mid && j <= high) {
			if (a[i] < a[j]) tmp[k++] = a[i++];
			else tmp[k++] = a[j++];
			}
		// 把左边剩余的数移入数组
		while (i <= mid) tmp[k++] = a[i++];
		// 把右边边剩余的数移入数组
		while (j <= high) tmp[k++] = a[j++];
		// 把新数组中的数覆盖nums数组
		for (int t = 0; t < tmp.length; t++) {
			a[t + low] = tmp[t];
		}
	}

	public static void mergeSort(int[] a, int low, int high) {
		int mid = (low + high) / 2;
		if (low < high) {
			// 左边
			mergeSort(a, low, mid);
			// 右边
			mergeSort(a, mid + 1, high);
			// 左右归并
			merge(a, low, mid, high);
		}
	}
	
	//*********************************************
	public static void main(String[] args) {
        int[] a= { 51, 46, 20, 18, 65, 97, 82, 30, 77, 50 };
        System.out.println("before sorting: " + Arrays.toString(a));
		mergeSort(a, 0, a.length - 1);
		System.out.println("after sorting:  " + Arrays.toString(a));
	}
}