数据结构八种排序算法实现

1.冒泡排序

package com.leay;


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;


public class InsertSort {

    
    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;


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;


public class QuickSort {

    
    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;



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;



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;


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[] 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 bucket : bucketList) {
            for (int temp : bucket) {
                arr[i++] = temp;
            }
        }
        return arr;
    }
}

8.选择排序

package com.leay;


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;
    }
}