traversing through a list

im trying to traverse through a list 2 values at a time, but for some reason, its getting stuck in an infinite loop

i have:

list<mystruct> a, b; // defined, each guaranteed to have at least 1 value

a.insert(a.end(), b.begin(), b.end());
a.sort(mysort);
list<mystruct>::iterator it1 = a.begin(), it2 = it1// or = a.begin(), it doesnt seem to make a difference
it2++;

while(it2 != a.end()){// im not sure if this condition is correct; probably the error
    if (<condition>){
        // stuff
        a.erase(it2);
    } 
    else{
        it1++;
        it2++;
    }
}

say the combined list a is {1,2,3,3,开发者_C百科4,5,6,6,6,7} and that i am trying to remove duplicates. i am trying to get *i = 1 and *j = 2 at first and then shift down so *i = 2 and *j = 3. what did i do wrong in this code??

im new to c++ lists, so sorry if this question sounds silly

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You want to use it2 = a.erase(it2); otherwise it2 will be pointing to an element that you've erased from the list. a.erase returns the element following it2.

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Since your list appears to be sorted and you want to remove duplicates, use unique:

a.unique();

Then you don't have to mess with iterators, erasing, etc.

See http://www.cplusplus.com/reference/stl/list/unique/