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15. 3Sum
Medium
Given an integer array nums, return all the triplets [nums[i], nums[j], nums[k]] such that i != j, i != k, and j != k, and nums[i] + nums[j] + nums[k] == 0.
Notice that the solution set must not contain duplicate triplets.
Example 1:
Input: nums = [-1,0,1,2,-1,-4]
Output: [[-1,-1,2],[-1,0,1]]
Example 2:
Input: nums = []
Output: []
Example 3:
Input: nums = [0]
Output: []
Constraints:
0 <= nums.length <= 3000-105 <= nums[i] <= 105
Solution
# @param {Integer[]} nums
# @return {Integer[][]}
def three_sum(nums)
nums = nums.sort
rs = []
nums.each.with_index do |num, i|
if i > 0 && num == nums[i - 1]
next
end
l, r = i + 1, nums.size - 1
while l < r
sum = num + nums[l] + nums[r]
if sum > 0
r -= 1
elsif sum < 0
l += 1
else
rs << [num, nums[l], nums[r]]
l += 1
while nums[l] == nums[l - 1] && l < r
l += 1
end
end
end
end
rs
end