1 class Solution(object):
 2     def threeSumClosest(self, nums, target):
 3         """
 4         :type nums: List[int]
 5         :type target: int
 6         :rtype: int
 7         """
 8         size = len(nums)
 9         if size < 3:
10             return 0
11         nums.sort()
12         i = 0 # fix the first index
13         ans = nums[0] + nums[1] + nums[size - 1] # ans is used to record the solution
14         while i < size - 2:
15             tmp = target - nums[i]
16             j = i + 1
17             k = size - 1
18             while j < k:
19                 if nums[j] + nums[k] == tmp:
20                     return target
21                 if nums[j] + nums[k] > tmp:
22                     if nums[j] + nums[j + 1] >= tmp:
23                         if nums[j] + nums[j + 1] - tmp < abs(ans - target):
24                             ans = nums[i] + nums[j] + nums[j + 1]
25                         break
26                     tmpans = nums[i] + nums[j] + nums[k]
27                     if tmpans - target < abs(ans - target):
28                         ans = tmpans
29                     k -= 1
30                 else:
31                     if nums[k] + nums[k - 1] <= tmp:
32                         if tmp - nums[k] -nums[k - 1] < abs(ans - target):
33                             ans = nums[i] + nums[k - 1] + nums[k]
34                         break
35                     tmpans = nums[i] + nums[j] + nums[k]
36                     if target - tmpans < abs(ans - target):
37                         ans = tmpans
38                     j += 1
39             i += 1
40             if ans == target:
41                 return target
42         return ans