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public class Heapify {    public static void heapify(int[] arr) {        int length = arr.length;        for (int i = (length - 1) / 2; i >= 0; i--) {            shiftDown(arr, i);        }    }    //从索引为index的位置开始进行shiftdown操作    private static void shiftDown(int[] arr, int index) {        int length = arr.length;        while (2 * index + 1 < length) {            int left = 2 * index + 1;            int largest = left;            if (left + 1 < length && arr[left + 1] > arr[left]) {                largest = left + 1;            }                        if (arr[index] < arr[largest]) {                swap(arr, index, largest);            } else {                 break;            }            index = largest;        }    }    private static void swap(int[] arr, int i, int j) {        int temp = arr[i];        arr[i] = arr[j];        arr[j] = temp;    }    public static void main(String[] args) {        int[] arr = {3, 7, 5, 4, 1, 7, 9, 8, 5, 2};        heapify(arr);        for (int i : arr) {            System.out.print(i + " ");        }    }}

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