设计与分析提取法

Extract方法用于提取Heap的根元素。以下是算法。

Algorithm: Heap-Extract-Max (numbers[]) 
max = numbers[1] 
numbers[1] = numbers[heapsize] 
heapsize = heapsize – 1 
Max-Heapify (numbers[], 1) 
return max

例子

让我们考虑前面讨论的相同示例。现在我们要提取一个元素。该方法将返回堆的根元素。

删除根元素后，最后一个元素将被移动到根位置。

现在，Heapify 函数将被调用。Heapify之后，生成如下堆。

例子

C C++ Java Python


#include <stdio.h>
void swap(int arr[], int i, int j) {
    int temp = arr[i];
    arr[i] = arr[j];
    arr[j] = temp;
}
void maxHeapify(int arr[], int size, int i) {
    int leftChild = 2 * i + 1;
    int rightChild = 2 * i + 2;
    int largest = i;
    if (leftChild < size && arr[leftChild] > arr[largest])
        largest = leftChild;
    if (rightChild < size && arr[rightChild] > arr[largest])
        largest = rightChild;
    if (largest != i) {
        swap(arr, i, largest);
        maxHeapify(arr, size, largest); // Recursive call to continue heapifying
    }
}
int extractMax(int arr[], int *heapSize) {
    if (*heapSize < 1) {
        printf("Heap underflow!\n");
        return -1;
    }
    int max = arr[0];
    arr[0] = arr[*heapSize - 1];
    (*heapSize)--;
    maxHeapify(arr, *heapSize, 0); // Heapify the updated heap
    return max;
}
int main() {
    int arr[] = { 55, 50, 30, 40, 20, 15, 10 }; // Max-Heap
    int heapSize = sizeof(arr) / sizeof(arr[0]);
    int max = extractMax(arr, &heapSize); // Extract the max element from the heap
    printf("Extracted Max Element: %d\n", max);
    // Print the updated Max-Heap
    printf("Updated Max-Heap: ");
    for (int i = 0; i < heapSize; i++)
        printf("%d ", arr[i]);
    printf("\n");
    return 0;
}

输出

Extracted Max Element: 55
Updated Max-Heap: 50 40 30 10 20 15


#include <iostream>
#include <vector>
void swap(std::vector<int>& arr, int i, int j) {
    int temp = arr[i];
    arr[i] = arr[j];
    arr[j] = temp;
}
void maxHeapify(std::vector<int>& arr, int size, int i) {
    int leftChild = 2 * i + 1;
    int rightChild = 2 * i + 2;
    int largest = i;
    if (leftChild < size && arr[leftChild] > arr[largest])
        largest = leftChild;

    if (rightChild < size && arr[rightChild] > arr[largest])
        largest = rightChild;
    if (largest != i) {
        swap(arr, i, largest);
        maxHeapify(arr, size, largest); // Recursive call to continue heapifying
    }
}
int extractMax(std::vector<int>& arr, int& heapSize) {
    if (heapSize < 1) {
        std::cout << "Heap underflow!" << std::endl;
        return -1;
    }
    int max = arr[0];
    arr[0] = arr[heapSize - 1];
    heapSize--;
    maxHeapify(arr, heapSize, 0); // Heapify the updated heap
    return max;
}
int main() {
    std::vector<int> arr = { 55, 50, 30, 40, 20, 15, 10 }; // Max-Heap
    int heapSize = arr.size();
    int max = extractMax(arr, heapSize); // Extract the max element from the heap
    std::cout << "Extracted Max Element: " << max << std::endl;
    // Print the updated Max-Heap
    std::cout << "Updated Max-Heap: ";
    for (int i = 0; i < heapSize; i++)
        std::cout << arr[i] << " ";
    std::cout << std::endl;
    return 0;
}

输出

Extracted Max Element: 55
Updated Max-Heap: 50 40 30 10 20 15


import java.util.Arrays;
public class MaxHeap {
    public static void swap(int arr[], int i, int j) {
        int temp = arr[i];
        arr[i] = arr[j];
        arr[j] = temp;
    }
    public static void maxHeapify(int arr[], int size, int i) {
        int leftChild = 2 * i + 1;
        int rightChild = 2 * i + 2;
        int largest = i;
        if (leftChild < size && arr[leftChild] > arr[largest])
            largest = leftChild;
        if (rightChild < size && arr[rightChild] > arr[largest])
            largest = rightChild;
        if (largest != i) {
            swap(arr, i, largest);
            maxHeapify(arr, size, largest); // Recursive call to continue heapifying
        }
    }
    public static int extractMax(int arr[], int heapSize) {
        if (heapSize < 1) {
            System.out.println("Heap underflow!");
            return -1;
        }
        int max = arr[0];
        arr[0] = arr[heapSize - 1];
        heapSize--;
        maxHeapify(arr, heapSize, 0); // Heapify the updated heap
        return max;
    }
    public static void main(String args[]) {
        int arr[] = { 55, 50, 30, 40, 20, 15, 10 }; // Max-Heap
        int heapSize = arr.length;
        int max = extractMax(arr, heapSize); // Extract the max element from the heap
        System.out.println("Extracted Max Element: " + max);
        // Print the updated Max-Heap
        System.out.print("Updated Max-Heap: ");
        for (int i = 0; i < heapSize; i++)
            System.out.print(arr[i] + " ");
        System.out.println();
    }
}

输出

Extracted Max Element: 55
Updated Max-Heap: 50 40 30 10 20 15 10


def swap(arr, i, j):
    arr[i], arr[j] = arr[j], arr[i]
def max_heapify(arr, size, i):
    left_child = 2 * i + 1
    right_child = 2 * i + 2
    largest = i
    if left_child < size and arr[left_child] > arr[largest]:
        largest = left_child
    if right_child < size and arr[right_child] > arr[largest]:
        largest = right_child
    if largest != i:
        swap(arr, i, largest)
        max_heapify(arr, size, largest) # Recursive call to continue heapifying
def extract_max(arr, heap_size):
    if heap_size < 1:
        print("Heap underflow!")
        return -1
    max_element = arr[0]
    arr[0] = arr[heap_size - 1]
    heap_size -= 1
    max_heapify(arr, heap_size, 0) # Heapify the updated heap
    return max_element
arr = [55, 50, 30, 40, 20, 15, 10] # Max-Heap
heap_size = len(arr)
max_element = extract_max(arr, heap_size) # Extract the max element from the heap
print("Extracted Max Element:", max_element)
# Print the updated Max-Heap
print("Updated Max-Heap:", arr)

输出

Extracted Max Element: 55
Updated Max-Heap: [50, 40, 30, 10, 20, 15, 10]

设计与分析 提取法

例子

例子

输出

输出

输出

输出

设计与分析提取法