堆排序

package Sort;

public class Heap_Sort {
    static int heap_length ;
    public static void main(String[] args) {
        int []a = {16,14,10,8,7,9,3,2,4,1};
        int []b = new int [a.length+1]; 
        for(int i =0;i<a.length;i++){
            b[i+1] = a[i];
        }
        a = b;
//      heap_length = a.length-1;
        ShowArray(a);
        HEAPSORT(a);
        ShowArray(a);
    }
    //显示数组
    public static void ShowArray(int[]A){
        for(int i=1;i<A.length;i++){
            System.out.print(A[i]+" ");
        }
        System.out.println();
    }

    public static int PARENT(int i){//返回父节点
        return i/2;
    }

    public static int LEFT(int i){//返回左节点
        return i*2;
    }

    public static int RIGHT(int i){//返回右节点
        return  i*2+1;
    }

    public static void MAX_HEAPIFY(int []A, int i){//堆的维护
        int l = LEFT(i);
        int r = RIGHT(i);
        int largest;
        //比较父节点，左右子节点大小
        if(l<= heap_length && A[l]>A[i]){
            largest = l;
        }else{
            largest = i;
        }
        if(r<=heap_length && A[r]>A[largest]){
            largest = r;
        }
        //如果子节点比父节点大，则交换
        if(largest != i){
            int temp = A[i];
            A[i] = A[largest];
            A[largest] = temp;
            MAX_HEAPIFY(A, largest);
        }
    }
    /**
     * 建堆
     * @param A
     */
    public static void BUILD_MAX_HEAP(int []A){
        heap_length = A.length-1;
        for(int i = heap_length/2;i>=1;i--){//维护最小父节点
            MAX_HEAPIFY(A, i);
        }
    }
    public static void HEAPSORT(int []A){
        BUILD_MAX_HEAP(A);//建堆
        for(int i = heap_length;i>1;i--){
            int temp = A[1];
            A[1] = A[i];
            A[i] = temp;
            heap_length--;
            MAX_HEAPIFY(A, 1);
        }
    }
}