16-LeetCode15. 三数之和

双指针；

class Solution {
public:
    vector<vector<int>> threeSum(vector<int>& nums) {
        vector<vector<int>> res;
        sort(nums.begin(), nums.end());

        for(int i = 0; i < nums.size(); i++)
        {
            if(i > 0 && nums[i] == nums[i-1])    continue;
            for(int j = i + 1, k = nums.size() - 1; j < k; j++)
            {
                if(j > i + 1 && nums[j] == nums[j-1])    continue;
                while(j < k - 1 && nums[i] + nums[j] + nums[k-1] >= 0) k--;
                if(nums[i] + nums[j] + nums[k] == 0)
                {
                    res.push_back({nums[i], nums[j], nums[k]});
                }
            }
        }
        return res;
    }
};