push_heap (3C++std) - Tru64 UNIX
Standard C++ LibraryCopyright 1996, Rogue Wave Software, Inc.
NAME
push_heap - Places a new element into a heap.
SYNOPSIS
#include <algorithm>
template <class RandomAccessIterator>
void
push_heap(RandomAccessIterator first,
RandomAccessIterator last);
template <class RandomAccessIterator, class Compare>
void
push_heap(RandomAccessIterator first,
RandomAccessIterator last, Compare comp);
DESCRIPTION
A heap is a particular organization of elements in a range between two
random access iterators [a, b). Its two key properties are:
1. *a is the largest element in the range.
2. *a may be removed by the pop_heap algorithm, or a new element added by
the push_heap algorithm, in O(logN) time.
These properties make heaps useful as priority queues.
The push_heap algorithms uses the less than (<) operator as the default
comparison. As with all of the heap manipulation algorithms, an alternate
comparison function can be specified.
The push_heap algorithm is used to add a new element to the heap. First, a
new element for the heap is added to the end of a range. (For example, you
can use the vector or deque member function push_back()to add the element
to the end of either of those containers.) The push_heap algorithm assumes
that the range [first, last - 1) is a valid heap. It then properly
positions the element in the location last - 1 into its proper position in
the heap, resulting in a heap over the range [first, last).
Note that the push_heap algorithm does not place an element into the heap's
underlying container. You must user another function to add the element to
the end of the container before applying push_heap.
COMPLEXITY
For push_heap at most log(last - first) comparisons are performed.
EXAMPLE
//
// heap_ops.cpp
//
#include <algorithm>
#include <vector>
#include <iostream.h>
int main(void)
{
int d1[4] = {1,2,3,4};
int d2[4] = {1,3,2,4};
// Set up two vectors
vector<int> v1(d1,d1 + 4), v2(d2,d2 + 4);
// Make heaps
make_heap(v1.begin(),v1.end());
make_heap(v2.begin(),v2.end(),less<int>());
// v1 = (4,x,y,z) and v2 = (4,x,y,z)
// Note that x, y and z represent the remaining
// values in the container (other than 4).
// The definition of the heap and heap operations
// does not require any particular ordering
// of these values.
// Copy both vectors to cout
ostream_iterator<int,char> out(cout," ");
copy(v1.begin(),v1.end(),out);
cout << endl;
copy(v2.begin(),v2.end(),out);
cout << endl;
// Now let's pop
pop_heap(v1.begin(),v1.end());
pop_heap(v2.begin(),v2.end(),less<int>());
// v1 = (3,x,y,4) and v2 = (3,x,y,4)
// Copy both vectors to cout
copy(v1.begin(),v1.end(),out);
cout << endl;
copy(v2.begin(),v2.end(),out);
cout << endl;
// And push
push_heap(v1.begin(),v1.end());
push_heap(v2.begin(),v2.end(),less<int>());
// v1 = (4,x,y,z) and v2 = (4,x,y,z)
// Copy both vectors to cout
copy(v1.begin(),v1.end(),out);
cout << endl;
copy(v2.begin(),v2.end(),out);
cout << endl;
// Now sort those heaps
sort_heap(v1.begin(),v1.end());
sort_heap(v2.begin(),v2.end(),less<int>());
// v1 = v2 = (1,2,3,4)
// Copy both vectors to cout
copy(v1.begin(),v1.end(),out);
cout << endl;
copy(v2.begin(),v2.end(),out);
cout << endl;
return 0;
}
Output :
4 2 3 1
4 3 2 1
3 2 1 4
3 1 2 4
4 3 1 2
4 3 2 1
1 2 3 4
1 2 3 4
WARNING
If your compiler does not support default template parameters, you need to
always supply the Allocator template argument. For instance, you will need
to write :
vector<int, allocator<int> >
instead of :
vector<int>
SEE ALSO
make_heap, pop_heap, sort_heap
STANDARDS CONFORMANCE
ANSI X3J16/ISO WG21 Joint C++ Committee
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