Sum Algorithm: O(n^2) in average [closed]

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I have n numbers (could be a list or array of n numbers).

Given a number k I want to return a quadruplet of numbers (a,b,c,d) thus that a+b+c+d=k.

Tim开发者_如何学编程e Complexity: O(n^2) in average (probability).

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You might find this useful: http://en.wikipedia.org/wiki/Dynamic_programming

Think about how to break the problem into subproblems.