手撕堆排序 优先级队列的实现方式

package 排序;

import common.Utils;

public class HeapSort {

    public static void Adjust(int[] arr,int startIndex,int len){
        int childIndex = 0;
        int threshold = len-1;
        for(;2*startIndex+1<len;startIndex = childIndex){
            childIndex = 2*startIndex+1;
            //if childIndex = len-1,then arr[childIndex+1] = arr[len],
            //which is ArrayIndexOutofBoundsException
            if(childIndex<threshold && arr[childIndex]<arr[childIndex+1])
                childIndex++;
            if(arr[childIndex]>arr[startIndex]){
                Utils.swap(arr, startIndex, childIndex);
            }else {
                break;
            }
        }
    }
    
    public static void heapSort(int[] arr){
        long start = System.nanoTime();
        int midIndex = arr.length/2-1;
        //初始化堆
        for(int i = midIndex;i>=0;i--){
            Adjust(arr, i, arr.length);
        }
        
        //调整堆
        for(int i=arr.length-1;i>=1;i--){
            Utils.swap(arr, 0, i);
            Adjust(arr, 0, i);
        }
        long end = System.nanoTime();
        System.out.println("runtime:"+(end-start)/1e6);
    }
    
    public static void main(String[] args) {
        int[] arr = Utils.produceNum(0, 1000000, 600000);
        System.out.println("before heapSort");
        //Utils.displayByOneLine(arr);
        heapSort(arr);
        System.out.println("after heapSort");
        //Utils.displayByOneLine(arr);
    }
}