From 0206b7d3990593a6364fc9149db114aa8dc493e6 Mon Sep 17 00:00:00 2001
From: majinliang <18233698150@163.com>
Date: Thu, 5 May 2016 23:45:22 +0800
Subject: [PATCH] 4

---
 MergeSortTest.java | 78 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 78 insertions(+)
 create mode 100644 MergeSortTest.java

diff --git a/MergeSortTest.java b/MergeSortTest.java
new file mode 100644
index 0000000..0aa3b01
--- /dev/null
+++ b/MergeSortTest.java
@@ -0,0 +1,78 @@
+package mergesort;
+public class MergeSortTest {
+
+	public static void main(String[] args) {
+		int[] data = new int[] { 5, 3, 6, 2, 1, 9, 4, 8, 7 };
+		mergeSort(data);
+		System.out.println("排序后的数组：");
+		print(data);
+	}
+
+	public static void mergeSort(int[] data) {
+		sort(data, 0, data.length - 1);
+	}
+
+	public static void sort(int[] data, int left, int right) {
+		if (left >= right)
+			return;
+		// 找出中间索引
+		int center = (left + right) / 2;
+		// 对左边数组进行递归
+		sort(data, left, center);
+		// 对右边数组进行递归
+		sort(data, center + 1, right);
+		// 合并
+		merge(data, left, center, right);
+	}
+
+	/**
+	 * 将两个数组进行归并，归并前面2个数组已有序，归并后依然有序
+	 * 
+	 * @param data
+	 *            数组对象
+	 * @param left
+	 *            左数组的第一个元素的索引
+	 * @param center
+	 *            左数组的最后一个元素的索引，center+1是右数组第一个元素的索引
+	 * @param right
+	 *            右数组最后一个元素的索引
+	 */
+	public static void merge(int[] data, int left, int center, int right) {
+		// 临时数组
+		int[] tmpArr = new int[data.length];
+		// 右数组第一个元素索引
+		int mid = center + 1;
+		// third 记录临时数组的索引
+		int third = left;
+		// 缓存左数组第一个元素的索引
+		int tmp = left;
+		while (left <= center && mid <= right) {
+			// 从两个数组中取出最小的放入临时数组
+			if (data[left] <= data[mid]) {
+				tmpArr[third++] = data[left++];
+			} else {
+				tmpArr[third++] = data[mid++];
+			}
+		}
+		// 剩余部分依次放入临时数组（实际上两个while只会执行其中一个）
+		while (mid <= right) {
+			tmpArr[third++] = data[mid++];
+		}
+		while (left <= center) {
+			tmpArr[third++] = data[left++];
+		}
+		// 将临时数组中的内容拷贝回原数组中
+		// （原left-right范围的内容被复制回原数组）
+		while (tmp <= right) {
+			data[tmp] = tmpArr[tmp++];
+		}
+	}
+
+	public static void print(int[] data) {
+		for (int i = 0; i < data.length; i++) {
+			System.out.print(data[i] + "\t");
+		}
+		System.out.println();
+	}
+
+}
\ No newline at end of file