Leetcode#15 3Sum

class Solution {
    public:
        vector<vector<int>> threeSum(vector<int>& nums) {
            vector<vector<int>> res;
            if (nums.size() < 3)
                return res;

            sort(nums.begin(), nums.end());
            for (int i=0; i<nums.size(); i++) {
                /* exclude duplicated target */
                if (i > 0 && nums[i] == nums[i-1])
                    continue;

                int target = 0 - nums[i];
                int left = i+1;
                int right = nums.size()-1;
                while (left < right) {
                    if (target == nums[left] + nums[right]) {
                        vector<int> ans;
                        ans.push_back(nums[i]);
                        ans.push_back(nums[left]);
                        ans.push_back(nums[right]);
                        res.push_back(ans);
                        left++;
                        right--;
                        while (left < nums.size() && nums[left] == nums[left-1])
                            left++;
                        while (right > 0 && nums[right] == nums[right+1])
                            right--;
                    } else {
                        if (target > nums[left] + nums[right]) {
                            left++;
                        } else {
                            right--;
                        }
                    }
                }
            }
            return res;
        }
};