Algorithms - Priceton - 02 - 3-Sum

3-Sum : Given N distinct integers, how many triples sum to exactly zero?

---------------------------------------------------------------------------------------

3-Sum : brute-force algorithm O(N³)

---------------------------------------------------------------------------------------

3-Sum : sorting-based algorithm O(N²lgN)

• sort the numbers.O(NlgN)
• for each pair of numbers a[i] and a[j], binary search for -(a[i]+a[j]). O(N²lgN)