冒泡排序、选择排序（java版）

图解说明可以参考https://blog.youkuaiyun.com/qq_31702609/article/details/81293023

java版冒泡排序代码如下

import java.util.Arrays;

public class BubbleSort {
    //way=1 为升序 way=2为降序
    public static void sort(int[] arr, int way) {
        int temp;
        if (way == 1) {
            for (int i = 0; i < arr.length - 1; i++) {
                for (int j = 0; j < arr.length - i - 1; j++) {
                    if (arr[j] > arr[j + 1]) {
                        temp = arr[j];
                        arr[j] = arr[j + 1];
                        arr[j + 1] = temp;
                    }
                }
                System.out.println("第"+(i+1)+"趟排序的结果："+ Arrays.toString(arr));
            }
        }
        if (way == 2) {
            for (int i = 0; i < arr.length - 1; i++) {
                for (int j = 0; j < arr.length - i - 1; j++) {
                    if (arr[j] < arr[j + 1]) {
                        temp = arr[j];
                        arr[j] = arr[j + 1];
                        arr[j + 1] = temp;
                    }
                }
                System.out.println("第"+(i+1)+"趟排序的结果："+ Arrays.toString(arr));
            }
        }
    }

    //改进版
    //思路：如果在某一轮比较中没有一次交换，则可以提前终止
    public static void sortUpgrade(int[] arr, int way) {
        int temp;
        if (way == 1) {
            for (int i = 0; i < arr.length - 1; i++) {
                int count = 0;
                for (int j = 0; j < arr.length - i - 1; j++) {
                    if (arr[j] > arr[j + 1]) {
                        temp = arr[j];
                        arr[j] = arr[j + 1];
                        arr[j + 1] = temp;
                        count++;
                    }
                }
                if (count==0)
                    break;
                System.out.println("第"+(i+1)+"趟排序的结果："+ Arrays.toString(arr));
            }
        }
        if (way == 2) {
            for (int i = 0; i < arr.length - 1; i++) {
                int count = 0;
                for (int j = 0; j < arr.length - i - 1; j++) {
                    if (arr[j] < arr[j + 1]) {
                        temp = arr[j];
                        arr[j] = arr[j + 1];
                        arr[j + 1] = temp;
                        count++;
                    }
                }
                if (count==0)
                    break;
                System.out.println("第"+(i+1)+"趟排序的结果："+ Arrays.toString(arr));
            }
        }
    }
}

java版的选择排序代码如下

import java.util.Arrays;

public class SelecSort {
    public static void sort(int[] arr) {
        int max;
        int temp;
        for (int i = 0; i < arr.length - 1; i++) {
            int index = i;
            max = arr[i];
            for (int j = i + 1; j < arr.length; j++) {
                if (arr[j] > max) {
                    max = arr[j];
                    index = j;
                }
            }
            temp = arr[i];
            arr[i] = arr[index];
            arr[index] = temp;
        }
    }
}