数据结构八种排序算法实现

数据结构八种排序算法实现

1.冒泡排序

package com.leay;

/**
 * 冒泡排序实现
 *
 * @author x@leay
 * @date 2021-12-09 17:00
 **/
public class BubbleSort {

    public static int[] sort(int[] arr) {
        for (int i = arr.length - 1; i > 0; i--) {
            for (int j = 0; j <= i - 1; j++) {
                if (arr[j] > arr[i]) {
                    swap(arr, i, j);
                }
            }
        }
        return arr;
    }

    public static void swap(int[] arr, int i, int j) {
        int swap = arr[i];
        arr[i] = arr[j];
        arr[j] = swap;
    }

    public static void print(int[] arr) {
        String printStr = "";
        for (int i : arr) {
            printStr = printStr + i + ",";
        }
        System.out.println(printStr);
    }


    public static void main(String[] args) {
        Random random = new Random(0);
        random.ints(-100, 100);
        int[] arr = new int[20];

        for (int i = 0; i < arr.length; i++) {
            arr[i] = random.nextInt(100);
        }
        print(arr);
        print(sort(arr));
    }
}

2.插入排序

package com.leay;

import java.util.Objects;
/**
 * 插入排序实现
 *
 * @author x@leay
 * @date 2021-12-09 21:37
 **/

public class InsertSort {

    /**
     * 从后往前插入
     */
    public static int[] sort(int[] arr) {
        if (Objects.isNull(arr) || arr.length <= 1) {
            return arr;
        }
        for (int i = 1; i < arr.length; i++) {
            int j = i - 1;
            while (j >= 0 && arr[j] > arr[j + 1]) {
                swap(arr, j, j + 1);
                j--;
            }
        }
        return arr;
    }
}

3.希尔排序

package com.leay;

/**
 * 希尔排序实现
 *
 * @author x@leay
 * @date 2021-12-10 23:08
 **/
public class ShellSort {
    // 相邻间隔有序
    public static int[] sort(int[] arr) {
        for (int gap = arr.length / 2; gap > 0; gap /= 2) {
            for (int i = gap; i < arr.length; i++) {
                int j = i;
                while (j - gap >= 0 && arr[j - gap] > arr[j]) {
                    Utils.swap(arr, j - gap, j);
                    j = j - gap;
                }
            }
        }
        return arr;
    }
}

4.快速排序

package com.leay;

/**
 * 快速排序
 *
 * @author x@leay
 * @date 2021-12-09 22:00
 **/
public class QuickSort {

    /**
     * 快速排序原理
     * 1.找到数组中一个节点在数组中的位置那么当前节点在数组中的顺序就确定了
     * 2.利用分治算法用1的方式处理当前节点前面的数组和当前节点后面位置的数组
     */
    public static void sort(int[] arr, int left, int right) {
        if (left > right) {
            return;
        }
        // 去除当前最后一个元素
        int temp = arr[right];
        int l = left;
        int r = right - 1;
        // 当前l比temp大 r比temp小
        while (l <= r) {
            while (l <= r && arr[r] > temp) {
                r--;
            }
            while (l <= r && arr[l] < temp) {
                l++;
            }

            if (l <= r) {
                swap(arr, l, r);
                l++;
                r--;
            }
        }
        swap(arr, l, right);
        sort(arr, left, l - 1);
        sort(arr, l + 1, right);
    }
}

5.归并排序

package com.leay;


/**
 * 归并排序
 *
 * @author x@leay
 * @date 2021-12-10 01:02
 **/
public class MergeSort {

    public static int[] sort(int[] arr, int low, int high) {
        if (low >= high) {
            return arr;
        }
        int mid = (high + low) / 2;
        sort(arr, low, mid);
        sort(arr, mid + 1, high);
        int[] temp = new int[high - low + 1];
        int left = low;
        int right = mid + 1;
        int cur = 0;
        while (left <= mid && right <= high) {
            if (arr[left] < arr[right]) {
                temp[cur++] = arr[left++];
            } else if (arr[left] > arr[right]) {
                temp[cur++] = arr[right++];
            } else {
                temp[cur++] = arr[left++];
                temp[cur++] = arr[right++];
            }
        }
        while (left <= mid) {
            temp[cur++] = arr[left++];
        }
        while (right <= high) {
            temp[cur++] = arr[right++];
        }
        for (int i = 0; i < temp.length; i++) {
            arr[i + low] = temp[i];
        }
        return arr;
    }
}

6.堆排序

package com.leay;


/**
 * 堆排序算法实现
 *
 * @author x@leay
 * @date 2021-12-10 21:55
 **/
public class HeapSort {

    // 创建一个大根堆
    public static int[] heapInsert(int[] arr) {
        // 比parent节点大的往上走
        int parent;
        for (int i = 0; i < arr.length; i++) {
            parent = (i - 1) / 2;
            while (i > 0 && arr[parent] < arr[i]) {
                swap(arr, parent, i);
                i = parent;
                parent = (parent - 1) / 2;
            }
        }
        return arr;
    }

    // 当前节点的子节点的最大值是否大于当前父节点如果大于就交换
    public static void heapAdjust(int[] arr, int end) {
        int parent = 0;
        while (parent < end) {
            int maxSon = 2 * parent + 1 >= end ? parent : 2 * parent + 2 >= end
                    || arr[2 * parent + 1] > arr[2 * parent + 2] ? 2 * parent + 1 : 2 * parent + 2;
            int max = arr[maxSon] > arr[parent] ? maxSon : parent;
            if (max == parent) {
                break;
            }
            swap(arr, parent, max);
            parent = max;
        }
    }

    public static int[] sort(int[] arr) {
        if (arr.length <= 1) {
            return arr;
        }
        heapInsert(arr);
        swap(arr, 0, arr.length - 1);
        for (int i = arr.length - 1; i > 1; i--) {
            heapAdjust(arr, i);
            swap(arr, 0, i - 1);
        }
        return arr;
    }
}

7.桶排序

package com.leay;

import java.util.ArrayList;
import java.util.List;

/**
 * 桶排序
 *
 * @author x@leay
 * @date 2021-12-11 00:06
 **/
public class BucketSort {


    public static int[] sort(int[] arr) {

        int min = Integer.MAX_VALUE;
        int max = Integer.MIN_VALUE;

        // 计算桶的个数
        for (int i : arr) {
            min = Math.min(min, i);
            max = Math.max(max, i);
        }
        int size = max - min + 1;
        // 初始化桶
        ArrayList<Integer>[] bucketList = new ArrayList[size];
        for (int i = 0; i < size; i++) {
            bucketList[i] = new ArrayList();
        }
        // 元素放到指定的桶中
        for (int item : arr) {
            int index = item-min;
            bucketList[index].add(item);
        }
        int i = 0;
        for (ArrayList<Integer> bucket : bucketList) {
            for (int temp : bucket) {
                arr[i++] = temp;
            }
        }
        return arr;
    }
}

8.选择排序

package com.leay;

/**
 * 选择排序
 *
 * @author x@leay
 * @date 2021-12-09 21:56
 **/
public class SelectionSort {

    public static int[] sort(int[] arr) {
        for (int i = arr.length - 1; i >= 1; i--) {
            for (int j = i - 1; j >= 0; j--) {
                if (arr[j] > arr[i]) {
                    swap(arr, i, j);
                }
            }
        }
        return arr;
    }
}