归并排序Java

归并排序（Java）

博客说明

文章所涉及的资料来自互联网整理和个人总结，意在于个人学习和经验汇总，如有什么地方侵权，请联系本人删除，谢谢！

归并排序介绍

归并排序（MERGE-SORT）是利用归并的思想实现的排序方法，该算法采用经典的分治（divide-and-conquer）策略（分治法将问题分(divide)成一些小的问题然后递归求解，而治(conquer)的阶段则将分的阶段得到的各答案"修补"在一起，即分而治之)。

代码

package cn.guizimo.sort;import java.util.Arrays;public class MergetSort {    public static void main(String[] args) {        int arr[] = {8, 4, 5, 7, 1, 3, 6, 2};        int temp[] = new int[arr.length];        System.out.println("排序前");        System.out.println(Arrays.toString(arr));        mergeSort(arr, 0, arr.length - 1, temp);        System.out.println("排序后");        System.out.println(Arrays.toString(arr));    }    public static void mergeSort(int[] arr, int left, int right, int[] temp) {        if (left < right) {            int mid = (left + right) / 2;            mergeSort(arr, left, mid, temp);            mergeSort(arr, mid + 1, right, temp);            merge(arr, left, mid, right, temp);        }    }    public static void merge(int[] arr, int left, int mid, int right, int[] temp) {        int i = left;        int j = mid + 1;        int t = 0;        while (i <= mid && j <= right) {            if (arr[i] <= arr[j]) {                temp[t] = arr[i];                t += 1;                i += 1;            } else {                temp[t] = arr[j];                t += 1;                j += 1;            }        }        while (i <= mid) {            temp[t] = arr[i];            t += 1;            i += 1;        }        while (j <= right) {            temp[t] = arr[j];            t += 1;            j += 1;        }        t = 0;        int tempIndex = left;        while (tempIndex <= right) {            arr[tempIndex] = temp[t];            t += 1;            tempIndex += 1;        }    }}

测试

速度测试

package cn.guizimo.sort;import java.util.Arrays;public class MergetSort {    public static void main(String[] args) {        int max = 80000;        int[] arr = new int[max];        for (int i = 0; i < max; i++) {            arr[i] = (int)(Math.random() * 8000000);        }        int temp[] = new int[arr.length];        long date1 = System.currentTimeMillis();        mergeSort(arr, 0, arr.length - 1, temp);        long date2 = System.currentTimeMillis();        System.out.println("归并排序"+max+"数组的时间为："+(date2-date1));    }    public static void mergeSort(int[] arr, int left, int right, int[] temp) {        if (left < right) {            int mid = (left + right) / 2;            mergeSort(arr, left, mid, temp);            mergeSort(arr, mid + 1, right, temp);            merge(arr, left, mid, right, temp);        }    }    public static void merge(int[] arr, int left, int mid, int right, int[] temp) {        int i = left;        int j = mid + 1;        int t = 0;        while (i <= mid && j <= right) {            if (arr[i] <= arr[j]) {                temp[t] = arr[i];                t += 1;                i += 1;            } else {                temp[t] = arr[j];                t += 1;                j += 1;            }        }        while (i <= mid) {            temp[t] = arr[i];            t += 1;            i += 1;        }        while (j <= right) {            temp[t] = arr[j];            t += 1;            j += 1;        }        t = 0;        int tempIndex = left;        while (tempIndex <= right) {            arr[tempIndex] = temp[t];            t += 1;            tempIndex += 1;        }    }}

感谢

尚硅谷

万能的网络

以及勤劳的自己