题目
Given an array nums of n integers, are there elements a, b, c in nums such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero.
解题思路
先给数组排序，确定一个数，枚举另外两个数，注意去重，如果第一个数已经是正数了，则可以退出
代码
class Solution:
def threeSum(self, nums: List[int]) -> List[List[int]]:
n = len(nums)
nums.sort()
res = []
for i in range(n - 2):
if nums[i] > 0:
break
if i > 0 and nums[i] == nums[i - 1]:
continue
j, k = i + 1, n - 1
while j < k:
cur = nums[i] + nums[j] + nums[k]
if cur < 0:
j += 1
elif cur > 0:
k -= 1
else:
res.append([nums[i], nums[j], nums[k]])
while j + 1 < k and nums[j] == nums[j + 1]:
j += 1
while k - 1 > j and nums[k] == nums[k - 1]:
k -= 1
j += 1
k -= 1
return res
