几个排序算法

Posted 2021-01-03 liter7

emmm,这是给我自己看的。。。。

package com.gjjun.sorts;

import java.util.Arrays;

/**
 * @author gjjun
 * @date 2018/9/2
 **/
public class Sorts {
    public static void main(String[] args) {
        int[] array = {5, 2, 3, 6, 1, 4, 7, 8};
        Sorts sorts = new Sorts();

        //直接插入排序
//        sorts.insertSorts(array);

        //冒泡排序
//        sorts.bubbleSorts(array);

        //选择排序
//        sorts.selectSorts(array);

        //希尔排序
//        sorts.shellSorts(array);

        //快速排序
//        sorts.quickSorts(array);

        //堆排序
        sorts.heapSorts(array);
        System.out.println(Arrays.toString(array));
    }

    private void heapSorts(int[] array) {
        //1.建堆
        for (int i = array.length / 2 - 1; i >= 0; i--) {
            heapAdjust(array, i, array.length);
        }
        System.out.println(Arrays.toString(array));
        //2.筛选
        for (int i = array.length - 1; i > 0; i--) {
            swap(array, i, 0);
            heapAdjust(array, 0, i);
        }
    }

    private void heapAdjust(int[] array, int i, int l) {
        int rcTemp = array[i];
        for (int j = 2 * i + 1; j < l; j = j * 2 + 1) {
            if (j + 1 < l && array[j] < array[j + 1]) {
                j++;
            }
            if (array[j] > rcTemp) {
                array[i] = array[j];
                i = j;
            } else {
                break;
            }
        }
        array[i] = rcTemp;
    }

    private void quickSorts(int[] array) {
        qSorts(array, 0, array.length - 1);
    }

    private void qSorts(int[] array, int low, int high) {
        if (low < high) {
            int pivotLoc = partition(array, low, high);
            qSorts(array, low, pivotLoc - 1);
            qSorts(array, pivotLoc + 1, high);
        }
    }

    private int partition(int[] array, int low, int high) {
        int pivotKey = array[low];
        while (low < high) {
            while (low < high && array[high] >= pivotKey) {
                high--;
            }
            array[low] = array[high];
            while (low < high && array[low] <= pivotKey) {
                low++;
            }
            array[high] = array[low];
        }
        array[low] = pivotKey;
        return low;
    }

    private void shellSorts(int[] array) {
        int length = array.length;
        int temp;
        int gap = length / 2;
        while (gap > 0) {
            for (int i = gap; i < length; i++) {
                temp = array[i];
                int preIndex = i - gap;
                while (preIndex >= 0 && array[preIndex] > temp) {
                    array[preIndex + gap] = array[preIndex];
                    preIndex -= gap;
                }
                array[preIndex + gap] = temp;
            }
            gap /= 2;
        }
    }

    private void selectSorts(int[] array) {
        int length = array.length;

        for (int i = 0; i < length; i++) {
            int min = array[i];
            int index = i;
            for (int j = i + 1; j < length; j++) {
                if (array[j] < min) {
                    min = array[j];
                    index = j;
                }
            }
            swap(array, i, index);
        }

    }

    private void bubbleSorts(int[] array) {
        int length = array.length;
        for (int i = 0; i < length; i++) {
            for (int j = 0; j < length - i - 1; j++) {
                if (array[j] > array[j + 1]) {
                    swap(array, j, j + 1);
                }
            }
        }
    }

    private void swap(int[] array, int i, int j) {
        int temp = array[i];
        array[i] = array[j];
        array[j] = temp;
    }


    /**
     * 直接插入排序
     *
     * @param array
     */
    private void insertSorts(int[] array) {
        int length = array.length;
        for (int i = 1; i < length; i++) {
            int key = array[i];
            int j = i - 1;
            //后移
            while (j >= 0 && array[j] > key) {
                array[j + 1] = array[j];
                j--;
            }
            array[j + 1] = key;
        }
    }
}