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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
object Solution {
@SuppressWarnings(Array("scala:S3776"))
def threeSum(nums: Array[Int]): List[List[Int]] = {
val sortedNums = nums.sorted
var result: List[List[Int]] = List()
for (i <- 0 until sortedNums.length - 2) {
if (i == 0 || (i > 0 && sortedNums(i) != sortedNums(i - 1))) {
var left = i + 1
var right = sortedNums.length - 1
val target = -sortedNums(i)
while (left < right) {
if (sortedNums(left) + sortedNums(right) == target) {
result = List(sortedNums(i), sortedNums(left), sortedNums(right)) :: result
while (left < right && sortedNums(left) == sortedNums(left + 1))
left += 1
while (left < right && sortedNums(right) == sortedNums(right - 1))
right -= 1
left += 1
right -= 1
} else if (sortedNums(left) + sortedNums(right) < target)
left += 1
else
right -= 1
}
}
}
result
}
}