【数据结构和算法实践-排序-归并排序】

数据结构和算法实践-排序-归并排序

• • 题目
  • My Thought
  • 代码示例
  • • JAVA-8

题目

排序

My Thought

然后再进行递归，递归要注意两个方面：
一、自我调用
二、终止条件：即函数边界
注意点：树、递归*

代码示例

JAVA-8

    public class MergeSort {


    public static void mergeSort(int arr[]) {
        if (arr == null || arr.length < 2) {
            return;
        }
        process(arr, 0, arr.length - 1);
    }

    public static void process(int arr[], int left, int right) {

        if (left == right) {
            return;
        }
        int mid = (left + right) / 2;
        process(arr, left, mid);
        process(arr, mid, right);
        merge(arr, left, mid, right);

    }

    private static void merge(int[] arr, int left, int mid, int right) {
        int help[] = new int[right - left + 1];
        int i = 0;
        int p1 = left;
        int p2 = right;
        while (p1 <= left && p2 <= right) {
            help[i++] = arr[p1] <= arr[p2] ? arr[p1++] : arr[p2++];
        }
        while (p1 <= left) {
            help[i++] = arr[p1++];
        }
        while (p2 <= right) {
            help[i++] = arr[p2++];
        }
        for (i = 0; i < help.length; i++) {
            arr[left + i] = help[i];
        }

    }

}