Java implements commonly used sorting algorithms 1-bubble and selection sort

 bubble:

　 The basic idea of ​​bubbling is that for unordered data, the nested loop compares the size, and the time complexity is O(n^2);

package algorithm; 


/** 
* bubble sort, 
*/ 
public class BubbleSort { 

    public static void main(String[] args) { 
        int[] arr = {7, 9, 2, 6, 0, 3, 8}; 
        for (int i = 0; i < arr.length; i++) {//The outer loop controls the number of sorting passes 
            for (int j = i+1; j < arr.length; j++) {//The inner loop controls each How many times to sort 
                if (arr[i] > arr[j]) { 
                    int temp = arr[j]; 
                    arr[j] = arr[i]; 
                    arr[i] = temp; 
                } 
            } 
            for(int k :arr ){ 
                System.out.print(k+" "); 
            } 
            System.out.println("--"); 
        }
       for(int i :arr){
           System.out.println(i);
       }
    }
}

Selection sort:
 Compared with bubble sort, the number of necessary exchanges is reduced from O(n^2) to O(n); in selection sort, instead of only comparing two adjacent data, it is necessary to record a specified data
　　

public class SelectSort { 

    public static void selectionSort(int[] a) { 
        int n = a.length; 
        for (int i = 0; i < n; i++) { 
            int k = i; 
            // find the subscript of the minimum value 
            for (int j = i + 1; j < n; j++) { 
                if (a[j] < a[k]) { 
                    k = j; 
                } 
            } 
            // put minimum value at end of sorted sequence 
            if (k > i ) { 
                int tmp = a[i]; 
                a[i] = a[k]; 
                a[k] = tmp; 
            } 
            for (int g : a){ 
                System.out.print(g+ " ");} 
            System. out.println("------------");
        }
    }

    public static void main(String[] args) {
        int[] b = { 49, 38, 65, 97, 76, 13, 27, 50 };
        selectionSort(b);
        for (int i : b)
            System.out.print(i + " ");
    }
}