3Sum Smaller
Similar Problems:
- Series: TwoSum Problems & Follow-Up
- 3Sum Closest
- CheatSheet: Leetcode For Code Interview
- Tag: #twosum, #3sum
Given an array of n integers nums and a target, find the number of index triplets i, j, k with 0 <= i < j < k < n that satisfy the condition nums[i] + nums[j] + nums[k] < target.
For example, given nums = [-2, 0, 1, 3], and target = 2.
Return 2. Because there are two triplets which sums are less than 2:
[-2, 0, 1] [-2, 0, 3]
Follow up: Could you solve it in O(n^2) runtime?
Github: code.dennyzhang.com
Credits To: leetcode.com
Leave me comments, if you have better ways to solve.
## https://code.dennyzhang.com/3sum-smaller
## Basic Ideas: two pointer
## Complexity: Time O(n^2), Space O(1)
class Solution:
def threeSumSmaller(self, nums, target):
"""
:type nums: List[int]
:type target: int
:rtype: int
"""
nums.sort()
length = len(nums)
res = 0
for i in range(0, length-2):
l, r = i+1, length-1
while l<r:
v = nums[i]+nums[l]+nums[r]
if v < target:
res += (r-l)
l += 1
else:
r -= 1
return res
