堆排序

堆排序

给定数组创建一个最大堆或者最小堆然后进行排序，分为两个步骤，根据数组创建最大堆，然后堆排序

最大堆适用于升序，最小堆适用于降序

package everySort;

public class MaxHeapSort {
    public static void main(String[] args) {
            int arr[] = {4, 6, 8, 5, 9};
            sort(arr);
            for(int i : arr){
                System.out.print(i + " ");
            }
     }
     public static void sort(int[] nums){
        //根据数组找到第一个非叶子节点，就是 nums.length / 2 - 1
        for(int i = nums.length / 2 - 1; i >= 0; i--){
            //构建最大堆
            heapSort(nums, i, nums.length);
        }

        for(int j = nums.length - 1; j > 0 ; j--){
            swap(nums, 0, j);
            heapSort(nums, 0 , j);
        }
     }
    public static void heapSort(int[] arr, int i, int len){

        int k = 2 * i +1;
        int temp = arr[i];
        if(k < len - 1 && arr[k] < arr[k + 1]){
            k ++;
        }
        if(k < len && arr[k] > arr[i]){
            System.out.println("i :" + i + "-->k :" + k);
            arr[i] = arr[k];
            arr[k] = temp;
            i = k;
            //替换后点子节点要进行检查
            heapSort(arr, i, len);
        }
    }
    public static void swap(int arr[], int i, int j){
        int temp = arr[i];
        arr[i] = arr[j];
        arr[j] = temp;
    }
}

package everySort;

public class MinHeapSort {
    public static void main(String[] args) {
        int[] nums = {4, 6, 8, 5, 9};
        sort(nums);
        for(int j : nums){
            System.out.print(j + " ");
        }
    }
    public static void sort(int[] nums){
        //根据数组找到第一个非叶子节点，就是 nums.length / 2 - 1
        for(int i = nums.length / 2 - 1; i >= 0; i--){
            //构建最小堆
            heapSort(nums, i, nums.length);
        }
        for(int j = nums.length - 1; j > 0; j--){
            swap(nums, 0, j);
            heapSort(nums, 0, j);
        }

    }
    public static void heapSort(int[] nums, int i, int len){
        int k = 2 * i + 1;
        int temp = nums[i];
        if(k < len - 1 && nums[k] > nums[k + 1]){
            k ++;
        }
        if(k < len && nums[k] < nums[i]){
            nums[i] = nums[k];
            nums[k] = temp;
            i = k;
            heapSort(nums, i, len);
        }
    }
    public static void swap(int[] nums, int i, int j){
        int temp = nums[i];
        nums[i] = nums[j];
        nums[j] = temp;
    }
}