Microsoft KB Archive/157156

= STL Sample for the Predicate Versions of the heap Functions =

Article ID: 157156

Article Last Modified on 12/10/2003

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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 Q157156

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SUMMARY
The sample code below illustrates how to use the predicate versions of 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, class Compare> inline void make_heap(RandomAccessIterator first,                     RandomAccessIterator last,                      Compare compare)

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

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

template<class RandomAccessIterator, class Compare> inline void pop_heap(RandomAccessIterator first,                    RandomAccessIterator last,                     Compare compare) 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 ordered by the predicate. For example, if the predicate is greater, every element in the heap satisfies the following; every element is greater than or equal to its parent. The smallest element is stored in the root, and all children hold progressively larger values.

The make_heap function 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 predicate versions of the heap functions use the compare function for comparisons.

Sample Code
////////////////////////////////////////////////////////////////////// // // Compile options needed: /GX // // heap_functions.cpp : Illustrates how to use the predicate versions //                     of 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)

using namespace std;
 * 1) include
 * 2) include
 * 3) include
 * 4) 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, greater ) ; 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, greater ) ; 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 ;

make_heap(Numbers.begin, Numbers.end, greater ) ; //insert an element in the heap Numbers.push_back(7) ; push_heap(Numbers.begin, Numbers.end, greater ) ; cout << "After calling push_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, greater ) ; 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 { 4 10 69 10 30 70 96 100 } After calling sort_heap <pre class="fixed_text">Numbers { 100 96 70 69 30 10 10 4 } After calling push_heap <pre class="fixed_text">Numbers { 4 7 10 30 100 10 70 96 69 } After calling pop_heap <pre class="fixed_text">Numbers { 7 30 10 69 100 10 70 96 4 }

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