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Update: 0001-two-sum.py - add improved two-pass solution #5945

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Update: 0001-two-sum.py - add improved two-pass solution #5945

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23 changes: 23 additions & 0 deletions python/0001-two-sum.py
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Original file line number Diff line number Diff line change
@@ -1,3 +1,4 @@
# Hash Map (One Pass)
class Solution:
def twoSum(self, nums: List[int], target: int) -> List[int]:
prevMap = {} # val -> index
Expand All @@ -7,3 +8,25 @@ def twoSum(self, nums: List[int], target: int) -> List[int]:
if diff in prevMap:
return [prevMap[diff], i]
prevMap[n] = i


# Hash Map (Two Pass)
class Solution:
def twoSum(self, nums: List[int], target: int) -> List[int]:
indices = {} # val -> index

for i, n in enumerate(nums):
indices.setdefault(n, []).append(i)

for i, n in enumerate(nums):
diff = target - n

# Temporarily pop current num "n" from map
indices[n].remove(i)
result = indices.get(diff, [])
if result:
return [i, result[0]]

# If diff not found, add current num "n" back to map
indices[n].append(i)