Microsoft KB Archive/157157

= STL Sample for the heap Functions =

Article ID: 157157

Article Last Modified on 12/2/2003

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APPLIES TO

 The Standard C++ Library, when used with:  Microsoft Visual C++ 4.2 Professional Edition

 Microsoft Visual C++ 4.2 Enterprise Edition

 Microsoft Visual C++ 5.0 Learning Edition 

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This article was previously published under Q157157

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SUMMARY
The sample code below illustrates how to use the make_heap, sort_heap, push_heap, pop_heap, begin, and end STL functions in Visual C++.

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Prototype
template<class RandomAccessIterator> inline void make_heap(RandomAccessIterator first,                     RandomAccessIterator last)

template<class RandomAccessIterator> inline void sort_heap(RandomAccessIterator first,                     RandomAccessIterator last)

template<class RandomAccessIterator> inline void push_heap(RandomAccessIterator first,                     RandomAccessIterator last)

template<class RandomAccessIterator> inline void pop_heap(RandomAccessIterator first,                     RandomAccessIterator last) NOTE: The class/parameter names in the prototype do not match the original version in the header file. Some have been modified to improve readability.

Description
A heap is a sequence of elements organized like a binary tree. Each heap element corresponds to a tree node. The first value in the sequence [first..last) is the root, and is the largest value in the heap. Every element in the heap satisfies the following: every element is less than or equal to its parent. The largest element is stored in the root, and all children hold progressively smaller values.

The make_heap functions converts the range [first..last) into a heap.

The sort_heap function sorts a "heapified" sequence that was created using the make_heap function.

The push_heap function inserts a new value into the heap.

The pop_heap function swaps the first and last elements in the heap specified by [first, last), then reduces the length of the sequence by one before restoring the heap property.

The non-predicate versions of the heap functions use the operator< for comparisons.

Sample Code
////////////////////////////////////////////////////////////////////// // // Compile options needed: /GX // // heap_functions.cpp : Illustrates how to use the //                     make_heap, sort_heap, push_heap //                     and pop_heap functions. // // Functions: // //   make_heap : convert a sequence to a heap //   sort_heap : sort a heap //   push_heap : insert an element in a heap //   pop_heap  : remove the top element from a heap // // Written by Kalindi Sanghrajka // of Microsoft Product Support Services, // Software Core Developer Support. // Copyright (c) 1996 Microsoft Corporation. All rights reserved. //////////////////////////////////////////////////////////////////////

// disable warning C4786: symbol greater than 255 character, // okay to ignore
 * 1) pragma warning(disable: 4786)


 * 1) include
 * 2) include

using namespace std;
 * 1) include
 * 2) include

void main {   const int VECTOR_SIZE = 8 ;

// Define a template class vector of int typedef vector<int, allocator > IntVector ;

//Define an iterator for template class vector of strings typedef IntVector::iterator IntVectorIt ;

IntVector Numbers(VECTOR_SIZE) ;

IntVectorIt it ;

// Initialize vector Numbers Numbers[0] = 4 ; Numbers[1] = 10; Numbers[2] = 70 ; Numbers[3] = 10 ; Numbers[4] = 30 ; Numbers[5] = 69 ; Numbers[6] = 96 ; Numbers[7] = 100;

// print content of Numbers cout << "Numbers { " ; for(it = Numbers.begin; it != Numbers.end; it++) cout << *it << " " ; cout << " }\n" << endl ;

// convert Numbers into a heap make_heap(Numbers.begin, Numbers.end) ;

cout << "After calling make_heap\n" << endl ;

// print content of Numbers cout << "Numbers { " ; for(it = Numbers.begin; it != Numbers.end; it++) cout << *it << " " ; cout << " }\n" << endl ;

// sort the heapified sequence Numbers sort_heap(Numbers.begin, Numbers.end) ;

cout << "After calling sort_heap\n" << endl ;

// print content of Numbers cout << "Numbers { " ; for(it = Numbers.begin; it != Numbers.end; it++) cout << *it << " " ; cout << " }\n" << endl ;

//insert an element in the heap Numbers.push_back(7) ; push_heap(Numbers.begin, Numbers.end) ;

// you need to call make_heap to re-assert the // heap property make_heap(Numbers.begin, Numbers.end) ;

cout << "After calling push_heap and make_heap\n" << endl ;

// print content of Numbers cout << "Numbers { " ; for(it = Numbers.begin; it != Numbers.end; it++) cout << *it << " " ; cout << " }\n" << endl ;

// remove the root element from the heap Numbers pop_heap(Numbers.begin, Numbers.end) ;

cout << "After calling pop_heap\n" << endl ;

// print content of Numbers cout << "Numbers { " ; for(it = Numbers.begin; it != Numbers.end; it++) cout << *it << " " ; cout << " }\n" << endl ; } Program Output is: <pre class="fixed_text">Numbers { 4 10 70 10 30 69 96 100 } After calling make_heap <pre class="fixed_text">Numbers { 100 30 96 10 4 69 70 10 } After calling sort_heap <pre class="fixed_text">Numbers { 4 10 10 30 69 70 96 100 } After calling push_heap and make_heap <pre class="fixed_text">Numbers { 100 69 96 30 4 70 10 10 7 } After calling pop_heap <pre class="fixed_text">Numbers { 96 69 70 30 4 7 10 10 100 }

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