Re: Help: reverse a linked list

The best way to solve such problem is to do dry run.

p1.nextPtr = 0 ;
while (P3 != 0 )
{
    p2->nextPtr= p1;
    p1 = p2;
    if ( p3!= 0 ) p2 = p3;
    p3 = p3->nextPtr;
}
p2.nextptr = p1;

To see how list works, then its fine to try such code. To use in any
professional coding, go for STL list instead of creating a new one.

#include <list>
#include<iostream>

using std::cout;
using std::endl;

int main(int argc, char **argv)
{
     std::list<int> l1;
     l1.push_back(10);
     l1.push_back(20);
     l1.push_back(30);

     for( std::list<int>::const_iterator it = l1.begin(); it !=
l1.end() ; ++it)
     {
          cout <<"loop in same direction" <<*it<<endl;
     }
     for( std::list<int>::reverse_iterator it = l1.rbegin(); it !=
l1.rend() ; ++it)
     {
          cout <<"loop in opp direction" <<*it<<endl;
     }

// now actual reverse the list.. not just loop direction
     std::reverse(l1.begin() , l1.end());
     for( std::list<int>::const_iterator it = l1.begin(); it !=
l1.end() ; ++it)
     {
          cout <<"loop in same direction after reverse" <<*it<<endl;
     }
     for( std::list<int>::reverse_iterator it = l1.rbegin(); it !=
l1.rend() ; ++it)
     {
          cout <<"loop in opp direction reverse" <<*it<<endl;
     }
}

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