LeetCode/15_3Sum at master · KnowledgeCenterYoutube/LeetCode · GitHub

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Leetcode 15: 3Sum
Detailed Video explanation: https://youtu.be/Ca7k53qcTic

C++
---
vector<vector<int>> threeSum(vector<int>& nums) {
        int n = nums.size();
        if(n < 3) return {};
        vector<vector<int>> result;
        sort(nums.begin(), nums.end());
        for(int i = 0; i < n-2; ++i){
            if(i == 0 || nums[i] != nums[i-1]){
                int j = i + 1, k = n-1;
                while(j < k){
                    int sum = nums[i] + nums[j] + nums[k];
                    if(sum == 0){
                        result.push_back({nums[i], nums[j], nums[k]});
                        while(j < k && nums[j] == nums[j+1]) j++;
                        while(j < k && nums[k] == nums[k-1]) k--;
                        j++; k--;
                    }
                    else if (sum > 0) k--;
                    else j++;
                }
            }
        }
        return result;
    }

 Java:
 ----
 public List<List<Integer>> threeSum(int[] nums) {
        int n = nums.length;
        if(n < 3) return new ArrayList<List<Integer>>();
        List<List<Integer>> result = new ArrayList();
        Arrays.sort(nums);
        for(int i = 0; i < n-2; ++i){
            if(i == 0 || nums[i] != nums[i-1]){

                int j = i+1, k = n-1;
                while(j < k){
                    int sum = nums[i] + nums[j] + nums[k];
                    if(sum == 0) {
                        result.add(Arrays.asList(nums[i], nums[j], nums[k]));
                        while(j < k && nums[j] == nums[j+1]) j++;
                        while(j < k && nums[k] == nums[k-1]) k--;
                        j++; k--;
                    }
                    else if (sum < 0) j++;
                    else k--;
                }
            }
        }
        return result;
    }


 Python3:
 --------
 def threeSum(self, nums: List[int]) -> List[List[int]]:
        n = len(nums)
        if n < 3: return []
        result = []
        nums.sort()
        for i in range(n-2):
            if i == 0 or nums[i] != nums[i-1]:
                j,k = i+1, n-1
                while j < k:
                    sum = nums[i] + nums[j] + nums[k]
                    if sum == 0:
                        result.append([nums[i], nums[j], nums[k]])
                        while j < k and nums[j] == nums[j+1]: j += 1
                        while j < k and nums[k] == nums[k-1]: k -= 1
                        j, k = j+1, k-1
                    elif sum < 0: j += 1
                    else: k -= 1
        return result