五、排序算法（基础部分）

1、冒泡排序

 

 

package com.basicsort;

public class BubbleSort {
    public static void main(String[] args) {
        int[] arr = {3, 6, 7, 88, 5, 36, 22};
        int[] res = sort(arr);
        for (int data : res) {
            System.out.print(data + " ");
        }
    }

    //冒泡排序
    public static int[] sort(int[] arr) {
        boolean flag = false;
        int temp = 0;
        for (int i = 0; i < arr.length; i++) {
            for (int j = 0; j < arr.length - i - 1; j++) {
                if (arr[j] > arr[j + 1]) {
                    flag = true;//表示有交换
                    temp = arr[j];
                    arr[j] = arr[j + 1];
                    arr[j + 1] = temp;
                }
            }
            if(flag == false){//表示没有交换
                break;
            }else{
                flag = false;
            }
        }
        return arr;
    }
}

2、选择排序

 代码实现：

package com.basicsort;

public class SelectSort {
    public static void main(String[] args) {
        int[] arr = {3, 6, 7, 88, 5, 36, 22};
        int[] res = sort(arr);
        for (int data : res) {
            System.out.print(data + " ");
        }
    }

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

3、插入排序

 代码实现：

package com.basicsort;

public class InsertSort {
    public static void main(String[] args) {
        int[] arr = {3, 6, 7, 88, 5, 36, 22};
        int[] res = sort(arr);
        for (int data : res) {
            System.out.print(data + " ");
        }
    }

    public static int[] sort(int[] arr) {
        for (int i = 1; i < arr.length; i++) {
            int j = i;
            int targat = arr[j];
            while (j > 0 && arr[j - 1] > targat) {
                arr[j] = arr[j - 1];//往后移一位
                j--;
            }
            arr[j] = targat;
        }
        return arr;
    }
}

4、快速排序

 代码实现：

package com.basicsort;

public class QuickSort {
    public static void main(String[] args) {
        int[] arr = {3, 6, 7, 88, 5, 36, 22, 1};
        int[] res = sort(arr, 0, arr.length - 1);
        for (int data : res) {
            System.out.print(data + " ");
        }
    }

    public static int[] sort(int[] arr, int left, int right) {
        int l = left;
        int r = right;
        int midVal = arr[(left + right) / 2];
        while (l < r) {
            while (midVal > arr[l]) {
                l = l + 1;
            }
            while (midVal < arr[r]) {
                r = r - 1;
            }
            if (l >= r) {
                break;
            }
            int temp = arr[l];
            arr[l] = arr[r];
            arr[r] = temp;
            if (arr[l] == midVal) {
                r = r - 1;
            }
            if (arr[r] == midVal) {
                l = l + 1;
            }
        }
        if (l == r) {
            l = l + 1;
            r = r - 1;
        }
        if (left < r) {
            sort(arr, left, r);
        }
        if (right > l) {
            sort(arr, l, right);
        }

        return arr;
    }
}