- 3Sum Medium
3929
443
Favorite
Share 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.
Note:
The solution set must not contain duplicate triplets.
Example:
Given array nums = [-1, 0, 1, 2, -1, -4],
A solution set is: [ [-1, 0, 1], [-1, -1, 2] ]
思路：
- 两次循环加双指针，时间复杂度O(n^2)
代码：python3
1.class Solution:
class Solution:
def threeSum(self, nums):
nums.sort()
i, N, result = 0, len(nums), []
while i < N - 2:
j, k = i + 1, N - 1
while j < k:
Sum = nums[i] + nums[j] + nums[k]
if not Sum:
result.append([nums[i], nums[j], nums[k]])
while j < k and nums[j] == nums[j + 1]: j += 1
j += 1
while j < k and nums[k] == nums[k - 1]: k -= 1
k -= 1
elif Sum < 0:
while j < k and nums[j] == nums[j + 1]: j += 1
j += 1
else:
while j < k and nums[k] == nums[k - 1]: k -= 1
k -= 1
while i < N - 2 and nums[i] == nums[i + 1]: i += 1
i += 1
return result
