57. 3Sum Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero. Notice,

Elements in a triplet (a,b,c) must be in non-descending order. (ie, a ≤ b ≤ c)

The solution set must not contain duplicate triplets.

Example

For example, given array S = {-1 0 1 2 -1 -4}, A solution set is:

(-1, 0, 1)
(-1, -1, 2)

Python Solutions

class Solution:
    """
    @param: numbers: Give an array numbers of n integer
    @return: Find all unique triplets in the array which gives the sum of zero.
    """
    def threeSum(self, numbers):
        # write your code here
        ret = []
        n = len(numbers)
        numbers.sort()
        for pos in xrange(n - 2):
            if pos != 0 and numbers[pos] == numbers[pos - 1]:
                continue
            i, j = pos + 1, n - 1
            while i < j:
                if i != pos + 1 and numbers[i] == numbers[i - 1]:
                    i += 1
                    continue
                
                if j != n - 1 and numbers[j] == numbers[j + 1]:
                    j -= 1
                    continue
                
                if numbers[i] + numbers[j] == -numbers[pos]:
                    temp = [numbers[pos], numbers[i], numbers[j]]
                    temp.sort()
                    ret.append(temp)
                    i += 1
                    j -= 1
                elif numbers[i] + numbers[j] + numbers[pos] < 0:
                    i += 1
                else:
                    j -= 1
        return ret
    
    # Total Runtime: 454 ms
    # 100% test cases passed.