в 14:21, 25 мая 2010

2010-05-25T14:21:17Z

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==Demonstrating the STL vector push_back functions==

<source lang="cpp">#include <iostream>
#include <cassert>
#include <vector>
#include <string>
#include <algorithm> // for reverse
using namespace std;

int main()
{
string s("qwer");
vector<char> vector1(s.begin(), s.end());
vector<char> vector2;
vector<char>::iterator i;
for (i = vector1.begin(); i != vector1.end(); ++i)
vector2.push_back(*i);
for (i = vector2.begin(); i != vector2.end(); ++i)
cout << *i;
return 0;
}</source>
<pre class=codeResult>qwer</pre>

==Perform the heapsort with push_heap and pop_heap==

<source lang="cpp">#include <iostream>
using std::cout;
using std::endl;
#include <algorithm>
#include <vector>
#include <iterator>
int main()
{
int a[ 10 ] = { 3, 10, 2, 7, 4, 8, 1, 9, 5, 6 };
std::vector< int > v( a, a + 10 ); // copy of a
std::vector< int > v2;
std::ostream_iterator< int > output( cout, " " );
for ( int i = 0; i < 10; i++ )
{
v2.push_back( a[ i ] );
std::push_heap( v2.begin(), v2.end() );
cout << "\nv2 after push_heap(a[" << i << "]): ";
std::copy( v2.begin(), v2.end(), output );
}
for ( int j = 0; j < v2.size(); j++ )
{
cout << "\nv2 after " << v2[ 0 ] << " popped from heap\n";
std::pop_heap( v2.begin(), v2.end() - j );
std::copy( v2.begin(), v2.end(), output );
}
cout << endl;
return 0;
}</source>
<pre class=codeResult>v2 after push_heap(a[0]): 3
v2 after push_heap(a[1]): 10 3
v2 after push_heap(a[2]): 10 3 2
v2 after push_heap(a[3]): 10 7 2 3
v2 after push_heap(a[4]): 10 7 2 3 4
v2 after push_heap(a[5]): 10 7 8 3 4 2
v2 after push_heap(a[6]): 10 7 8 3 4 2 1
v2 after push_heap(a[7]): 10 9 8 7 4 2 1 3
v2 after push_heap(a[8]): 10 9 8 7 4 2 1 3 5
v2 after push_heap(a[9]): 10 9 8 7 6 2 1 3 5 4
v2 after 10 popped from heap
9 7 8 5 6 2 1 3 4 10
v2 after 9 popped from heap
8 7 4 5 6 2 1 3 9 10
v2 after 8 popped from heap
7 6 4 5 3 2 1 8 9 10
v2 after 7 popped from heap
6 5 4 1 3 2 7 8 9 10
v2 after 6 popped from heap
5 3 4 1 2 6 7 8 9 10
v2 after 5 popped from heap
4 3 2 1 5 6 7 8 9 10
v2 after 4 popped from heap
3 1 2 4 5 6 7 8 9 10
v2 after 3 popped from heap
2 1 3 4 5 6 7 8 9 10
v2 after 2 popped from heap
1 2 3 4 5 6 7 8 9 10
v2 after 1 popped from heap
1 2 3 4 5 6 7 8 9 10</pre>

==pop_back from a vector==

<source lang="cpp">#include <iostream>
#include <string>
#include <vector>
using namespace std;
int main()
{
vector<string> v;
v.push_back("A");
v.push_back("B");
v.push_back("C");
cout << v.size() << endl;
for (int i = 0; i < v.size(); ++i)
cout << v[i] << endl;
v[0] = "battle axe";
for (int i = 0; i < v.size(); ++i)
cout << v[i] << endl;
cout << v[0] << endl;
cout << v[0].size() << endl;
v.pop_back();
for (int i = 0; i < v.size(); ++i)
cout << v[i] << endl;
v.clear();
if (v.empty())
cout << "\nYou have nothing.\n";
else
cout << "\nYou have at least one item.\n";
return 0;
}</source>

==Using pop_back to Erase the Last Element==

<source lang="cpp">#include <iostream>
#include <vector>
int main ()
{
using namespace std;
vector <int> v;
v.push_back (50);
v.push_back (1);
v.push_back (987);
v.push_back (1001);
cout << "The vector contains ";
cout << v.size ();
cout << " elements before calling pop_back" << endl;
// Erase one element at the end
v.pop_back ();
cout << "The vector contains ";
cout << v.size ();
cout << " elements after calling pop_back" << endl;
cout << "Enumerating items in the vector... " << endl;
unsigned int nElementIndex = 0;
while (nElementIndex < v.size ())
{
cout << "Element at position " << nElementIndex << " is: ";
cout << v [nElementIndex] << endl;
// move to the next element
++ nElementIndex;
}
return 0;
}</source>

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в 14:21, 25 мая 2010

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