Re: comparing elements of vector<int> and list<int>
AnonMail2005@gmail.com wrote:
On Oct 9, 12:45 pm, arnuld <geek.arn...@gmail.com> wrote:
It is quite an ugly hack but it is all I am able to come up with for
now :-( and it does the requires work. I want to improve the program, I
know you people have much better ideas ;-)
/* C++ Primer - 4/e
*
* exercise 9.20
* STATEMENT:
* Write a program to to compare whether a vector<int> contains the
* same elements as a list<int>.
*
*/
#include <iostream>
#include <vector>
#include <list>
#include <algorithm>
#include <iterator>
int main()
{
std::cout << "Enter some integers for VECTOR: ";
std::vector<int> ivec;
std::copy( std::istream_iterator<int>( std::cin ),
std::istream_iterator<int>(),
std::back_inserter( ivec ) );
std::cin.clear();
std::cout << "Enter some integers for LIST: ";
std::list<int> ilist;
std::copy( std::istream_iterator<int>( std::cin ),
std::istream_iterator<int>(),
std::back_inserter( ilist ) );
std::cout << "\nNow we will compare VECTOR & LIST for equality :: ";
bool comp_result = true;
std::vector<int>::const_iterator viter = ivec.begin();
std::list<int>::const_iterator liter = ilist.begin();
/* If sizes are unequal, then they can not be equal :-) */
if( ivec.size() != ilist.size() )
{
comp_result = false;
}
else
{
for( ; ( viter != ivec.end() ) || ( liter != ilist.end() );
++viter, ++liter )
{
if( *viter != *liter )
{
comp_result = false;
}
}
}
if( comp_result )
{
std::cout << "VECTOR & LIST are EQUAL" << std::endl;
}
else
{
std::cout << "VECTOR & LIST are NOT equal" << std::endl;
}
return 0;
}
========= A FEW RUNS =================
~/programming/c++ $ g++ -ansi -pedantic -Wall -Wextra ex_09-20.cpp
~/programming/c++ $ ./a.out
Enter some integers for VECTOR: 1 2 3
Enter some integers for LIST: 1 2 1
Now we will compare VECTOR & LIST for equality :: VECTOR & LIST are NOT equal
~/programming/c++ $ ./a.out
Enter some integers for VECTOR: 1
Enter some integers for LIST: 1 2 3 4 5 6 7 8 9 0 9 9 8 8 8 8 8 8 8 8 8 8
8 8 8 88 88 88 8 8 8 88 8 8 88 8 8 8 8 8 8 8 8
Now we will compare VECTOR & LIST for equality :: VECTOR & LIST are NOT equal
~/programming/c++ $ ./a.out
Enter some integers for VECTOR: 1 2 3
Enter some integers for LIST: 1 2 3
Now we will compare VECTOR & LIST for equality :: VECTOR & LIST are EQUAL
~/programming/c++ $ ./a.out
Enter some integers for VECTOR: 1 2 3
Enter some integers for LIST: 1 2
Now we will compare VECTOR & LIST for equality :: VECTOR & LIST are NOT
equal
-- arnuldhttp://lispmachine.wordpress.com
You could also try std::equal for containers of the same length.
Also, your code should stop looping as soon as an element doesn't
match.
hth
So, it's easy to say:
if (ivec.size() != ilist.size())
return false;
else
return std::equal(ivec.begin(), ivec.end(), ilist.begin());
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