Standard C++ Library
Copyright 1998, Rogue Wave Software, Inc.
NAME
inplace_merge
- Merges two sorted sequences into one.
SYNOPSIS
#include <algorithm>
template <class BidirectionalIterator>
void inplace_merge(BidirectionalIterator first,
BidirectionalIterator middle,
BidirectionalIterator last);
template <class BidirectionalIterator, class Compare>
void inplace_merge(BidirectionalIterator first,
BidirectionalIterator middle,
BidirectionalIterator last,
Compare comp);
DESCRIPTION
The inplace_merge algorithm merges two sorted consecutive
ranges [first, middle) and [middle, last), and puts the
result of the merge into the range [first, last). The merge
is stable, which means that if the two ranges contain
equivalent elements, the elements from the first range
always precede the elements from the second.
There are two versions of the inplace_merge algorithm. The
first version uses the less than operator (operator<) as the
default for comparison, and the second version accepts a
third argument that specifies a comparison operator.
COMPLEXITY
When enough additional memory is available, inplace_merge
does at most (last - first) - 1 comparisons. If no addi-
tional memory is available, an algorithm with O(NlogN) com-
plexity (where N is equal to last-first) may be used.
EXAMPLE
//
// merge.cpp
//
#include <algorithm>
#include <vector>
#include <functional>
#include <iostream>
using namespace std;
int main()
{
int d1[4] = {1,2,3,4};
int d2[8] = {11,13,15,17,12,14,16,18};
// Set up two vectors
vector<int> v1(d1,d1 + 4), v2(d1,d1 + 4);
// Set up four destination vectors
vector<int> v3(d2,d2 + 8),v4(d2,d2 + 8),
v5(d2,d2 + 8),v6(d2,d2 + 8);
// Set up one empty vector
vector<int> v7;
// Merge v1 with v2
merge(v1.begin(),v1.end(),v2.begin(),v2.end(),
v3.begin());
// Now use comparator
merge(v1.begin(),v1.end(),v2.begin(),v2.end(),v4.begin(),
less<int>());
// In place merge v5
vector<int>::iterator mid = v5.begin();
advance(mid,4);
inplace_merge(v5.begin(),mid,v5.end());
// Now use a comparator on v6
mid = v6.begin();
advance(mid,4);
inplace_merge(v6.begin(),mid,v6.end(),less<int>());
// Merge v1 and v2 to empty vector using insert iterator
merge(v1.begin(),v1.end(),v2.begin(),v2.end(),
back_inserter(v7));
// Copy all cout
ostream_iterator<int,char> out(cout," ");
copy(v1.begin(),v1.end(),out);
cout << endl;
copy(v2.begin(),v2.end(),out);
cout << endl;
copy(v3.begin(),v3.end(),out);
cout << endl;
copy(v4.begin(),v4.end(),out);
cout << endl;
copy(v5.begin(),v5.end(),out);
cout << endl;
copy(v6.begin(),v6.end(),out);
cout << endl;
copy(v7.begin(),v7.end(),out);
cout << endl;
// Merge v1 and v2 to cout
merge(v1.begin(),v1.end(),v2.begin(),v2.end(),
ostream_iterator<int,char>(cout," "));
cout << endl;
return 0;
}
Program Output
1 2 3 4
1 2 3 4
1 1 2 2 3 3 4 4
1 1 2 2 3 3 4 4
11 12 13 14 15 16 17 18
11 12 13 14 15 16 17 18
1 1 2 2 3 3 4 4
1 1 2 2 3 3 4 4
WARNINGS
If your compiler does not support default template parame-
ters, then you always need to supply the Allocator template
argument. For instance, you have to write:
vector<int, allocator,int> >
instead of:
vector<int>
If your compiler does not support namespaces, then you do
not need the using declaration for std.
SEE ALSO
merge