static bool cmp(string &a,string &b)
{
    if(a.size()==b.size())
    {
        return a<b;
    }
    return a.size()<b.size();
}

This is a custom comparator to compare two strings that consist of big numbers, like "3922" and "12929", and compare them to see which is larger. However, I don't understand why when a.size() == b.size() we return a < b?

CodePudding user response：

if statement will execute only if the size of both strings is the same.(i.e "232" is equal to "934". but it will not execute for string-like ("2342", "234242").

and in the if statement you are comparing strings, not integers. so if want to compare integers then covert them first.

CodePudding user response：

Common algorithms in the standard library like std::lower_bound and std::sort make use of just one comparison function assumed to provide the result of a < b, which is enough to make all the other comparisons (if they need to test equality they can do !(a < b || b < a), for instance).

If this custom function didn't check the length of the strings, "1000" would come before "50" in lexicographical order, which is what std::string's operator<(...) uses (and what is used in that function when their length is equal).