排序效率，快排归并堆排Java实现

常见的排序时间复杂度与空间复杂度

排序原理动画

实现代码

快速排序

package com.leetcode.sort;

import java.util.Arrays;

/**
 * @Auther: Jibny Zhan
 * @Date: 2019/11/30 20:12
 * @Description:
 */
public class QuickSort {

    private static int count;

    private static void QuickSort(int[] num, int left, int right) {
        if (left >= right)
            return;
        int i = left;
        int j = right;
        int key = num[left];
        while (i < j) {
            if (num[j] >= key && i < j)
                j--;
            else if (num[i] <= key && i < j)
                i++;
            else {
                num[i] ^= num[j];
                num[j] ^= num[i];
                num[i] ^= num[j];
            }
        }
        num[left] = num[i];
        num[i] = key;
        count++;
        QuickSort(num, left, i - 1);
        QuickSort(num, i + 1, right);
    }

    public static void main(String[] args) {
        int[] num = {45, 3, 78, 64, 52, 11, 64, 55, 99, 11, 18};
        System.out.println(Arrays.toString(num));
        QuickSort(num, 0, num.length - 1);
        System.out.println(Arrays.toString(num));
        System.out.println("数组个数：" + num.length);
        System.out.println("循环次数：" + count);

    }

}

归并排序

package com.leetcode.sort;

import java.util.Arrays;

/**
 * @Auther: Jibny Zhan
 * @Date: 2019/12/1 00:42
 * @Description:
 */
public class MergeSort {

    private static void sort(int[] arr) {
        mergeSort(arr, 0, arr.length - 1);
    }
    
    //分割
    private static void mergeSort(int[] arr, int left, int right) {
        if (left == right)
            return;
        int mid = (left + right) >> 1;
        mergeSort(arr, left, mid);
        mergeSort(arr, mid + 1, right);
        merge(arr, left, mid, right);
    }

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

    public static void main(String[] args) {
        int[] nums = {2, 5, 3, 1, 10, 4, 6, 9};
        sort(nums);
        System.out.println(Arrays.toString(nums));
    }

}

堆排序

package com.leetcode.sort;

import java.util.Arrays;

/**
 * @Auther: Jibny Zhan
 * @Date: 2019/11/30 20:36
 * @Description:
 */
public class HeapSort {
    private static int count;

    //    1.调整堆
    public static void heapify(int[] tree, int n, int i) {
        if (i >= n)
            return;
        count++;
        int right = (i << 1) + 1;
        int left = (i << 1) + 2;
        int max = i;
        if (left < n && tree[left] > tree[max]) {
            max = left;
        }
        if (right < n && tree[right] > tree[max]) {
            max = right;
        }
        if (max != i) {
            swap(tree, i, max);
            heapify(tree, n, max);
        }
    }

    //    2.构建堆，从后往前调整堆
    public static void buildHeap(int[] tree, int n) {
        int lastNode = n - 1;
        int parent = (lastNode - 1) >> 1;
        int i = parent;
        for (i = parent; i >= 0; i--) {
            heapify(tree, n, i);
        }
    }

    //    3.交换堆顶和末尾元素
    public static void heapSort(int[] tree, int n) {
        buildHeap(tree, n);
        int i;
        for (i = n - 1; i >= 0; i--) {
            swap(tree, i, 0);
            heapify(tree, i, 0);
        }
    }

    public static void swap(int[] tree, int A, int B) {
        tree[A] ^= tree[B];
        tree[B] ^= tree[A];
        tree[A] ^= tree[B];
    }


    public static void main(String[] args) {
        int[] tree = {2, 5, 3, 1, 10, 4};
        heapSort(tree, tree.length);
        System.out.println(Arrays.toString(tree));
        System.out.println("循环次数：" + count);
    }
}

桶排序

package com.leetcode.sort;

import java.util.Arrays;

/**
 * @Auther: Jibny Zhan
 * @Date: 2019/11/30 21:47
 * @Description:
 */
public class BucketSort {
    public static int[] bucketSort(int[] nums, int maxNum){
        int[] sorted = new int[maxNum+1];

        for(int i=0; i<nums.length; i++){
            sorted[nums[i]] = nums[i];//把数据放到对应索引的位置
        }
        return sorted;
    }

    public static void main(String[] args) {
        int[] x = { 99, 65, 24, 47, 50, 88,33, 66, 67, 31, 18 };
        int[] sorted = bucketSort(x, 99);
        System.out.println(Arrays.toString(sorted));
    }

}

排序效率，快排归并堆排Java实现

原文：https://www.cnblogs.com/binjz/p/12501349.html