Leetcode 259. 3Sum Smaller

 1 class Solution(object):
 2     def threeSumSmaller(self, nums, target):
 3         """
 4         :type nums: List[int]
 5         :type target: int
 6         :rtype: int
 7         """
 8         nums.sort()
 9         n = len(nums)
10         ans = 0
11
12         for k in range(n):
13             i, j = k+1, n-1
14             while i<j:
15                 sum3 = nums[k] + nums[i] + nums[j]
16                 if sum3 < target:
17                     ans += j - i
18                     i += 1
19                 else:
20                     j -= 1
21         return ans