堆排序

// C++ program for implementation of Heap Sort

#include <iostream>

  

using namespace std;

  

// To heapify a subtree rooted with node i which is

// an index in arr[]. n is size of heap

void heapify( int arr[], int n, int i)

{

     int largest = i; // Initialize largest as root

     int l = 2*i + 1; // left = 2*i + 1

     int r = 2*i + 2; // right = 2*i + 2

  

     // If left child is larger than root

     if (l < n && arr[l] > arr[largest])

         largest = l;

  

     // If right child is larger than largest so far

     if (r < n && arr[r] > arr[largest])

         largest = r;

  

     // If largest is not root

     if (largest != i)

     {

         swap(arr[i], arr[largest]);

  

         // Recursively heapify the affected sub-tree

         heapify(arr, n, largest);

     }

}

  

// main function to do heap sort

void heapSort( int arr[], int n)

{

     // Build heap (rearrange array)

     for ( int i = n / 2 - 1; i >= 0; i--)

         heapify(arr, n, i);

  

     // One by one extract an element from heap

     for ( int i=n-1; i>=0; i--) //刪除操做的時候，移出去最後一個數據，而後總個數減小了一個


     {

         // Move current root to end

         swap(arr[0], arr[i]);//交換最後一個和第一個根位置的元素

  

         // call max heapify on the reduced heap

         heapify(arr, i, 0);//開始從新堆排序，

     }

}

  

/* A utility function to print array of size n */

void printArray( int arr[], int n)

{

     for ( int i=0; i<n; ++i)

         cout << arr[i] << " " ;

     cout << "\n" ;

}

  

// Driver program

int main()

{

     int arr[] = {12, 11, 13, 5, 6, 7};

     int n = sizeof (arr)/ sizeof (arr[0]);

  

     heapSort(arr, n);

  

     cout << "Sorted array is \n" ;

     printArray(arr, n);

}

 

https://www.geeksforgeeks.org/heap-sort/     代碼

https://www.bilibili.com/video/av12667435/   視頻講解

https://www.bilibili.com/video/av18980178/    視頻講解

 https://blog.csdn.net/u010452388/article/details/81283998  代碼步驟詳解

 

https://www.cnblogs.com/sjrb/p/10371613.html

https://www.cnblogs.com/chengxiao/p/6129630.html