常见排序算法

public class BubbleSort {

    public static void main(String[] args) {
        int [] arr = new int[] {2,5,12,8,23,90,34};
        sort(arr);
        Arrays.stream(arr).forEach(x->System.out.print(x+ " "));
    }
    
    public static void sort(int [] arr) {
        for(int j = arr.length-1 ; j>0;j--) {
            for(int i = 0 ; i<j; i++) {
                if(arr[i] > arr[i+1]) {
                    swap(arr, i, i+1);
                }
            }
        }
    }
    
    
    public static void swap(int [] arr , int i , int j) {
        int temp =  arr[i];
        arr[i] = arr[j];
        arr[j] = temp;
    }
}

public class SelectionSort {

    public static void main(String[] args) {
        int [] arr = new int[] {2,5,12,8,23,90,34};
        sort(arr);
        Arrays.stream(arr).forEach(x->System.out.print(x+ " "));
        
    }
    
    
    public static void sort(int [] arr ) {
        for(int i=0 ; i<arr.length; i++) {
            int min = i;
            for(int j=i+1;j<arr.length;j++) {
                min = arr[j]<arr[min]?j:min;
            }
            swap(arr, min, i);
        }
    }
    
    
    public static void swap(int [] arr , int i , int j) {
        int temp =  arr[i];
        arr[i] = arr[j];
        arr[j] = temp;
    }
    
}

public class InsertSort {

    public static void main(String[] args) {
        int [] arr = new int[] {2,5,12,8,23,90,34};
        sort(arr);
        Arrays.stream(arr).forEach(x->System.out.print(x+ " "));
    }
    
    public static void sort(int [] arr ) {
        for(int i=1;i<arr.length;i++) {
            int j=i;
            while(j>0 ) {
                if( arr[j] < arr[j-1]) {
                    swap(arr,j,j-1);
                }
                j--;
            }
        }
        
    }
    
    
    public static void swap(int [] arr , int i , int j) {
        int temp =  arr[i];
        arr[i] = arr[j];
        arr[j] = temp;
    }
}

public class MergeSort {

    public static void main(String[] args) {
        int [] arr = new int[] {2,5,12,8,23,90,34};
        sort(arr, 0 , arr.length-1);
        Arrays.stream(arr).forEach(x->System.out.print(x+ " "));
    }
    
    public static void sort(int[] arr , int L , int R) {
        if(L == R) {
            return ;
        }
        int mid = L+((R-L)>>1);
        sort(arr,L,mid);
        sort(arr,mid+1,R);
        merge(arr,L,mid,R);
    }

    private static void merge(int [] arr, int L, int mid, int R) {
        int [] help = new int[R-L+1];
        int i = 0;
        int p1 = L;
        int p2 = mid+1;
        while(p1<=mid && p2<= R) {
            help[i++] =  arr[p1] < arr[p2]  ? arr[p1++]:arr[p2++];
        }
        while(p1<=mid) {
            help[i++] = arr[p1++];
        }
        while(p2<=R) {
            help[i++] = arr[p2++];
        }
        for(i= 0 ; i<help.length; i++ ) {
            arr[L+i] = help[i];
        }
    }

}