LC - 15. 3Sum

// Approach 1 (using set)
class Solution {
public:
    vector<vector<int>> threeSum(vector<int>& nums) 
    {
        if(!nums.size() || nums.size() < 3) return {};
        set<vector<int>> temp;
        vector<vector<int>> ans;
        sort(nums.begin(), nums.end());
        for(int i = 0; i <= nums.size()-3; i++)
        {
            int target = -nums[i];
            int lo = i+1;
            int hi = nums.size() -1;
            while(lo < hi)
            {
                if(nums[lo] + nums[hi] == target) 
                {
                    temp.insert({nums[i], nums[lo], nums[hi]});
                    lo++;
                    hi--;
                }
                else if(nums[lo] + nums[hi] < target) lo++;
                else hi--;
            }
        }
        for(auto v : temp) ans.push_back(v);
        return ans;
    }
};

// approach 2
class Solution {
public:
    vector<vector<int>> threeSum(vector<int>& nums) 
    {
        if(!nums.size() || nums.size() < 3) return {};
        vector<vector<int>> ans;
        sort(nums.begin(), nums.end());
        for(int i = 0; i <= nums.size()-3; i++)
        {
            int target = -nums[i];
            int lo = i+1;
            int hi = nums.size() -1;
            while(lo < hi)
            {
                if(nums[lo] + nums[hi] == target) 
                {
                    vector<int> v(3,0);
                    v[0] = nums[i];
                    v[1] = nums[lo];
                    v[2] = nums[hi];
                    ans.push_back(v);
                    while(lo < hi && nums[lo] == v[1] ) lo++;
                    while(hi > lo && nums[hi] == v[2] ) hi--;
                }
                else if(nums[lo] + nums[hi] < target) lo++;
                else hi--;
                
            }
            while(i+1 < nums.size() && nums[i+1] == nums[i] ) i++;
        }
        return ans;
    }
};