堆排序

堆排序

时间复杂度O(nlogn)
import java.util.Arrays;

public class Code_03_HeapSort {
    public static void heapSort(int []arr){
        if(arr==null||arr.length<2){
            return;
        }
        for (int i = 0; i < arr.length; i++) {
            heapInsert(arr,i);
        }
        int size=arr.length;
        swap(arr,0,--size);
        while (size>0){
            heapify(arr,0,size);
            swap(arr,0,--size);
        }
    }



    private static void heapInsert(int[] arr, int index) {
        while (arr[index]>arr[(index-1)/2]){
            swap(arr,index,(index-1)/2);
            index=(index-1)/2;
        }
    }
    private static void swap(int[] arr, int i, int j) {
        int temp=arr[i];
        arr[i]=arr[j];
        arr[j]=temp;

    }
    private static void heapify(int[] arr, int index, int size) {
        int left =index*2+1;
        while (left<size){
            int largest=left+1<size&&arr[left+1]>arr[left]?left+1:left;
            largest=arr[largest]>arr[index]?largest:index;
            if (largest==index){
                break;
            }
            swap(arr,largest,index);
            index=largest;
            left=index*2+1;
        }
    }
    public static void comparator(int []arr){
        Arrays.sort(arr);
    }

    //for test
    public static int []generateRandomArray(int maxSize,int maxValue){
        int []arr=new int[(int)((maxSize+1)*Math.random())];
        for (int i = 0; i < arr.length; i++) {
            arr[i]=(int)((maxValue+1)*Math.random())-(int)((maxValue)*Math.random());

        }
        return arr;
    }
    //for test
    public static int []copyArray(int []arr){
        if(arr==null){
            return null;
        }
        int []res=new int[arr.length];
        for (int i = 0; i < arr.length; i++) {
            res[i]=arr[i];

        }
        return res;

    }
    //for test
    public static boolean isEqual(int []arr1,int []arr2){
        if((arr1==null)&&(arr2!=null)||(arr1!=null&&arr2==null)){
            return false;
        }
        if(arr1==null&&arr2==null){
            return true;
        }
        if(arr1.length!=arr2.length){
            return false;
        }
        for (int i = 0; i < arr1.length; i++) {
            if(arr1[i]!=arr2[i]){
                return false;
            }

        }
        return  true;
    }
    public static void printArray(int []arr){
        if(arr==null){
            return;
        }
        for (int i = 0; i < arr.length; i++) {
            System.out.print(arr[i]+" ");


        }
        System.out.println();
    }

    public static void main(String[] args) {
        int testTime=50000;
        int maxSize=100;
        int maxValue=100;
        boolean succeed=true;
        for (int i = 0; i < testTime; i++) {
            int []arr1=generateRandomArray(maxSize,maxValue);
            int []arr2=copyArray(arr1);
            heapSort(arr1);
            comparator(arr2);
            if (!isEqual(arr1,arr2)){
                succeed=false;
                printArray(arr1);
                printArray(arr2);
                break;
            }
        }
        System.out.println(succeed?"Nicd !":"Fucking fucked!");

        int []arr=generateRandomArray(maxSize,maxValue);
        printArray(arr);
        heapSort(arr);
        printArray(arr);
    }

}

;

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