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leetcode 015

admin 11月 13, 2020 0

3 SUM
My first solution
My second solution

3 SUM

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.

Note: 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]
]

My first solution

Set one number and use to node to move, but this method is Time limited. The time consuming is N square plus NlogN.

class Solution(object):
    def threeSum(self, nums):
        """
        :type nums: List[int]
        :rtype: List[List[int]]
        """
        length = len(nums)
        nums.sort()
        res = []
        
        for i in range(length-2):
            if nums[i] > 0: break
            if i >= 1 and nums[i] == nums[i-1]:
                continue
            p = i + 1
            q = length - 1
            while p != q:
                s = nums[i] + nums[p] + nums[q]
                if s == 0:
                    if [nums[i],nums[p],nums[q]] not in res:
                         res.append([nums[i],nums[p],nums[q]])
                    p += 1
                elif s > 0:
                    q -= 1
                else:
                    p += 1
        return res

My second solution

Use the code of 2Sum.