数据结构与算法--->基础篇冒泡，选择，插入，希尔

冒泡排序-----基础排序算法

public class maopao {
    public static void main(String[] args) {
        int[] arr={123,4,8,6,3,7,8,9,10,45,89,57,45,75,26,78};
        for (int i = 1; i <arr.length-1; i++) {
            for (int j=0;j<arr.length-i;j++){
                if (arr[j]>arr[j+1]){
                    int temp=arr[j];
                    arr[j]=arr[j+1];
                    arr[j+1]=temp;
                }
            }
        }
        for (int i = 0; i < arr.length; i++) {
            System.out.print(arr[i]+",");
        }
    }
}

运行结果：3,4,6,7,8,8,9,10,26,45,45,57,75,78,89,123,

每次循环，找出最大值，下一次可以少循环一次

选择排序------与冒泡排序原理基本相同

public class xuanze {
    public static void main(String[] args) {
        int[] arr ={1,8,56,7,78,89,64,7,5,3,4,98};
        for (int i = 0; i < arr.length; i++) {
            for(int j=i+1;j<arr.length;j++){
                int max =arr[i];
                if (arr[j]<max){
                    int temp;
                    temp=arr[i];
                    arr[i]=arr[j];
                    arr[j]=temp;
                }
            }
        }
        System.out.println(Arrays.toString(arr));

    }
}

运行结果：[1, 3, 4, 5, 7, 7, 8, 56, 64, 78, 89, 98]

此处优化数组循环遍历改为Arrats.ToString.sout--->回车快捷键遍历数组更方便

 

插入排序

插入排序思想：数组从第i位开始,向前遍历使前方数组保持有序，直到数组遍历结束，数组变为有序数组

public class charu {
    public static void main(String[] args) {
        int[] arr={5,6,9,7,12,54,68,78,49,15,75,58,15,75};
        for (int i = 1; i < arr.length; i++) {
            for (int j = i; j >0 ; j--) {
                if (arr[j]<arr[j-1]){
                    swap(arr,j,j-1);
                }
            }
        }
        //数组遍历循环优化，减少代码
        System.out.println(Arrays.toString(arr));
    }
    //交换代码，简化直接调用
    public static void swap(int[] arr,int i, int j){
        int t=arr[i];
        arr[i]=arr[j];
        arr[j]=t;
    }
}

输出结果：[5, 6, 7, 9, 12, 15, 15, 49, 54, 58, 68, 75, 75, 78]

希尔排序------>缩小增量排序

public class xier {
    public static void main(String[] args) {
        int[] arr={2,5,8,7,9,78,18,35,48,62,58};
        xiE(arr);
    }
    public static void xiE(int[] arr){
        int leagth=0;
        while(leagth<(arr.length)/3){
            leagth=(leagth*3)+1;
            System.out.println(leagth);
        }
        for (int h = leagth; h >0; h=(h-1)/3) {
            for (int i = h; i <arr.length ; i++) {
                for (int j = i; j >h-1 ; j-=h) {
                    if (arr[j]<arr[j-h]){
                        swap(arr,j,j-h);
                    }
                }
            }
        }
        System.out.println(Arrays.toString(arr));
    }
    public static void swap(int[] arr,int i,int j){
        int t=arr[i];
        arr[i]=arr[j];
        arr[j]=t;
    }
}

运行结果：[2, 5, 7, 8, 9, 18, 35, 48, 58, 62, 78]

通过增量不断变小，数组逐渐变得有序，增量为一是原理与插入排序一样