LeetCode: 15. 3Sum

LeetCode: 15. 3Sum

Problem: 15. 3Sum

Link: https://leetcode.com/problems/3sum/

Difficulty: Medium

Description:

Given an array nums of n integers, are there elements a, b, c in nums such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero.

Note: The solution set must not contain duplicate triplets.

Example:

Given array nums = [-1, 0, 1, 2, -1, -4],

A solution set is:[[-1, 0, 1],[-1, -1, 2] ]

Solution:

Language: Swift

Runtime: 240ms
Memory: 22.6MB

Copy to Clipboard

class Solution {
    func threeSum(_ nums: [Int]) -> [[Int]] {
        if nums.count < 3 {
            return []
        }
        
        let nums = nums.sorted()
        var result : [[Int]] = []
        
        for i in 0 ..< nums.count - 2 {
            if nums[i] + nums[i + 1] + nums[i + 2] > 0 {
                break
            }
            
            if nums[i] + nums[nums.count - 1] + nums[nums.count - 2] < 0 {
                continue
            }
            
            if i > 0 && nums[i] == nums[i - 1] {
                continue
            }
            
            var target = -nums[i]
            var left = i + 1
            var right = nums.count - 1
            
            while left < right {
                if nums[left] + nums[right] == target {
                    result.append([nums[i], nums[left], nums[right]])
                    left += 1
                    right -= 1
                    
                    while left < right && nums[left] == nums[left - 1] {
                        left += 1
                    }
                    while left < right && nums[right] == nums[right + 1] {
                        right -= 1
                    }
                } else if nums[left] + nums[right] < target {
                    left += 1
                } else {
                    right -= 1
                }
            }
        }
        return result
    }
}

Related Posts

Leave A Comment Cancel reply