title: tricky linked list problem
body: <p>Given three lists: A, B and C of length n each. if any 3 three numbers (1 from each list), sum up to zero return true.I want to solve this with o(n)complexity.I have sorted the lists and I can think of creating either a hash map with sum of 2 linked lists or comparing 3 lists together[o(n*n*n)].Suggest some ways to improvise the methods to reduce complexity..I can't think of any...Thanks in adv</p>