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three_sum.py
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three_sum.py
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from typing import List
# two sum method
def threeSum(nums: List[int]) -> List[List[int]]:
nums.sort()
ans = []
lookup = dict()
for i, n in enumerate(nums):
lookup[n] = i
l = len(nums)
for i, n in enumerate(nums):
if i > 0 and n == nums[i - 1]:
continue
twosum = - n
if i + 1 <= l:
for j in range(i + 1, l):
tar = twosum - nums[j]
r = [n, nums[j], tar]
if j != i + 1 and nums[j] == nums[j - 1]:
continue
if tar in lookup and lookup[tar] > j:
ans.append(r)
return ans
# two pointer method
def threeSum(nums: List[int]) -> List[List[int]]:
ans = []
ln = len(nums)
if nums or ln < 3:
nums.sort()
for i, n in enumerate(nums):
l = i + 1
r = ln - 1
if i > 0 and n == nums[i - 1]:
continue
while l < r:
if (n + nums[l] + nums[r]) > 0:
r -= 1
elif (n + nums[l] + nums[r]) < 0:
l += 1
else:
ans.append([n, nums[l], nums[r]])
l += 1
while l < r and nums[l + 1] == nums[l]:
l += 1
return ans
lis = [-1,0,1,2,-1,-4]
print(threeSum(lis))