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| """
Three sum
find 3 integers summing closest to a target,
return their sum
Input: nums = [-1,2,1,-4], target = 1
Output: 2
Explanation: The sum that is closest to the target is 2. (-1 + 2 + 1 = 2).
"""
def threeSumClosest(self, nums: List[int], target: int) -> int:
"""
sort the list
for each num:
start left and right pointers at 0 and n-1
if left + right + num is target return
if the sum is closer, update the result
if less then sum, move left, else move right
"""
n = len(nums)
nums.sort()
res = None
resdif = float("inf")
for i,num in enumerate(nums):
# skip dups
if i>0 and num==nums[i-1]:
continue
l = i+1
r = n-1
while l<r:
total = num + nums[l] + nums[r]
if total == target:
return target
# update diff
diff = abs(total-target)
if diff < resdif:
res = total
resdif = diff
if total < target:
l += 1
else:
r -= 1
return res
|