归并排序

package test;

public class MergeSort {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		int[] arr = { 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 };
		System.out.println("排序前：");
		printArr(arr);
		sort(arr);
		System.out.println("排序后：");
		printArr(arr);
	}

	private static void sort(int[] arr) {
		int[] tmp = new int[arr.length];
		sort(arr, 0, arr.length - 1, tmp);

	}

	private static void sort(int[] arr, int left, int right, int[] tmp) {

		if (left < right) {
			int mid = (left + right) / 2;
			sort(arr, left, mid, tmp);
			sort(arr, mid + 1, right, tmp);
			merge(arr, left, mid, right, tmp);
		}
	}

	private static void merge(int[] arr, int left, int mid, int right, int[] tmp) {
		int i = left;
		int j = mid + 1;
		int t = 0;

		while (i <= mid && j <= right) {
			if (arr[i] <= arr[j]) {
				tmp[t++] = arr[i];
				i++;
			} else {
				tmp[t++] = arr[j];
				j++;
			}

		}
		for (; i <= mid; i++) {
			tmp[t++] = arr[i];

		}
		for (; j <= right; j++) {
			tmp[t++] = arr[j];

		}

		// 将tmp前t个数据拷贝到arr的Left至right的位置中；
		System.arraycopy(tmp, 0, arr, left, t);

		printArr(arr);

		// 清空；
		for (i = 0; i < tmp.length; i++) {
			tmp[i] = 0;
		}
	}

	/**
	 * 打印；
	 * 
	 * @param arr
	 */
	private static void printArr(int[] arr) {
		for (int i : arr) {
			System.out.print(i + " ");
		}
		System.out.println();
	}

}

运行

结果