three_sum
three_sum.py 源码
from typing import List
# 三数之和
class Solution:
# 暴力法，三层循环
# 超出时间限制
def threeSum_1(self, nums: List[int]) -> List[List[int]]:
res, s = [], set()
for i in range(len(nums) - 2):
for j in range(i + 1, len(nums) - 1):
for k in range(j + 1, len(nums)):
if nums[i] + nums[j] == -nums[k]:
t = tuple(sorted((nums[i], nums[j], nums[k])))
if t not in s:
res.append([nums[i], nums[j], nums[k]])
s.add(t)
return res
# 排序之后，使用双指针
def threeSum_2(self, nums: List[int]) -> List[List[int]]:
nums.sort()
res = []
for i, v in enumerate(nums):
if v > 0:
break
if i > 0 and nums[i] == nums[i - 1]:
continue
j, k = i + 1, len(nums) - 1
while j < k:
if nums[j] + nums[k] < -v:
j += 1
elif nums[j] + nums[k] > -v:
k -= 1
else:
res.append([nums[i], nums[j], nums[k]])
j, k = j + 1, k - 1
while j < k and nums[j] == nums[j - 1]:
j += 1
while j < k and nums[k] == nums[k + 1]:
k -= 1
return res
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