how to compare the two lists?

[zhangyhbais]

I want to compare the two lists. If there is difference, print out the error message. How should I do to make the computer's cost least?

For example:
list<string> coll_1: a, b ,c, d, e, f, g
list<string> coll_2: b, d, i, s

[jyfcsdn]

使用这两个函数
template<class InputIterator1, class InputIterator2>
bool equal(
InputIterator1 _First1,
InputIterator1 _Last1,
InputIterator2 _First2
);
template<class InputIterator1, class InputIterator2, class BinaryPredicate>
bool equal(
InputIterator1 _First1,
InputIterator1 _Last1,
InputIterator2 _First2,
BinaryPredicate _Comp
);

#include <list>
#include <iostream>
using namespace std;
int main(int argc, char* argv[])
{

list<string> coll_1;//: a, b ,c, d, e, f, g
list<string> coll_2;//: b, d, i, s

coll_1.push_back("a");
coll_1.push_back("b");

coll_2.push_back("a");
coll_2.push_back("a");


if( ( coll_1.empty() || coll_2.empty() )
|| ( coll_1.size() != coll_2.size() ) )
{
cout << "Not Equal" << endl;
}
else
{
if(!equal(coll_1.begin(), coll_1.end(), coll_2.begin()))
{
cout << "Not Equal" << endl;
}
}

return 0;
}

[begginginstorm]

If just to known whether the two lists are equal, you can use std::equal algorithm, which is included in <algorithm> header.

For example:
list<string> coll1;
list<string> coll2;
coll1.push_back("1");
coll1.push_back("2");
coll2.push_back("3");
coll2.push_back("4");
if(coll1.size() == coll2.size)
{
if(std::equal(coll1.begin(), coll1.end(), coll2.begin())
cout << "The two lists are equel" << endl;
else
cout << "The two lists are not equel " << endl;
}
else
{
cout << "The two lists are not equel " << endl;
}

[begginginstorm]

For:jyfcsdn
if( ( coll_1.empty() || coll_2.empty() )
|| ( coll_1.size() != coll_2.size() ) )
{
cout << "Not Equal" << endl;
}
It's not right. The following is better perhaps.
if( !(coll1.size() == coll2.size() && coll1.size() > 0) )
{
cout << "Not equal" << endl;
}

[jyfcsdn]

To begginginstorm
yes, u are right. It excutes more effectively.