冒泡排序选择排序插入排序

package com.smile.test.sort.bubble;

/**
 * 冒泡排序  时间复杂度O(n^2)
 */

public class Bubble {
    static void sort(Comparable[] a){
        for (int i = a.length-1; i>0; i--){
            for (int j=0; j<i; j++){
                if(greater(a[j],a[j+1])){
                    changeIndex(a, j, j+1);
                }
            }

        }
    }
    private static boolean greater(Comparable a,Comparable b){
        return a.compareTo(b) > 0;
    }
    private static void changeIndex(Comparable[] a,int i,int j){
        Comparable temp;
        temp = a[i];
        a[i] = a[j];
        a[j] = temp;
    }
}

import java.util.Arrays;

public class BubbleTest {
    public static void main(String[] args) {
        Integer[] a = {6,5,4,3,2,1};
        Bubble.sort(a);
        System.out.println(Arrays.toString(a));
    }
}

[1, 2, 3, 4, 5, 6]

Process finished with exit code 0

---

选择排序

public class Selections {
    static void sort(Comparable[] a){
        for (int i = 0; i <= a.length - 2; i++){
            int minIndex = i;
            for (int j = i+1; j < a.length; j++){
                if (greater(a[minIndex], a[j])){
                    minIndex = j;
                }
            }
            changeIndex(a, minIndex,i);
        }
    }
    // 比较a,b的大小
    private static boolean greater(Comparable a,Comparable b){
        return a.compareTo(b) > 0;
    }
    // 交换索引i 和 索引j处的值
    private static void changeIndex(Comparable[] a,int i,int j){
        Comparable temp;
        temp = a[i];
        a[i] = a[j];
        a[j] = temp;
    }
}

import java.util.Arrays;

public class SelectionsTest {
    public static void main(String[] args) {
        Integer[] arr = {4,5,8,9,6,3,1};
        Selections.sort(arr);
        System.out.println(Arrays.toString(arr));
    }
}

[1, 3, 4, 5, 6, 8, 9]

Process finished with exit code 0

---

插入排序

public class InsertSort {
    public static void sort(Comparable[] a){
        for (int i = 1; i < a.length; i++){
            for(int j = i; j>0; j--){
                if (greater(a[j-1], a[j])){
                    changeIndex(a,j-1,j);
                }
            }
        }
    }
    // 比较a,b的大小
    private static boolean greater(Comparable a,Comparable b){
        return a.compareTo(b) > 0;
    }
    // 交换索引i 和 索引j处的值
    private static void changeIndex(Comparable[] a,int i,int j){
        Comparable temp;
        temp = a[i];
        a[i] = a[j];
        a[j] = temp;
    }
}

import java.util.Arrays;

public class InsertTest {
    public static void main(String[] args) {
        Integer[] a = {4,3,2,10,12,1,5,6};
        InsertSort.sort(a);
        System.out.println(Arrays.toString(a));
    }
}

[1, 2, 3, 4, 5, 6, 10, 12]

Process finished with exit code 0