3Sum

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]
]

class Solution {
public:
    vector<vector<int>> threeSum(vector<int>& nums) {
      
        vector<vector<int> > res;
        vector<int> tempres;
        if(nums.empty())
            return res;
        if(nums.size()==1)
            return res;
        sort(nums.begin(), nums.end());
        for(int i=0; i<nums.size()-2; i++)
        {
            if (i > 0 && nums[i] == nums[i - 1]) continue;
            int start =i+1;
            int end = nums.size()-1;
            int sum = nums[i];
            while(start<end)
            {
                if((nums[start]+nums[end])==-sum)
                {
                    tempres.push_back(nums[i]);
                    tempres.push_back(nums[start]);
                    tempres.push_back(nums[end]);
                    res.push_back(tempres);
                    while( start< end && nums[start] == nums[start + 1]) ++start;
                    while (start< end && nums[end] == nums[end - 1]) --end;
                    tempres.clear();
                    ++start;
                    --end;
                    
                }else if((nums[start]+nums[end])>-sum)
                {
                    --end;
                }else
                {
                    ++start;
                }
            }
        }
       
        return res;
        
    }
};