How can I use lambda for container comparison operator ?

Question

This is how I would use inbuilt function or new class as a custom comparator

priority_queue< int, vector, greater > third (myints         


        

Answer 1

First define the lambda:

auto compareFunc = [](int a, int b) { return a > b; };

Then use decltype:

typedef priority_queue<int, vector<int>, decltype(compareFunc)> q2;

Now when you use q2, pass in the function:

q2 myQueue(compareFunc);

Basically, priority_queue takes the type of a function as it's 3rd template argument, while the constructor takes a pointer to that function itself.