[LeetCode] 15. 3Sum

Given an array S of n integers, are there elements a, b, c in S 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.

For example, given array S = [-1, 0, 1, 2, -1, -4],A solution set is:[  [-1, 0, 1],  [-1, -1, 2]]

   vector<vector<int>> threeSum(vector<int>& nums) {        vector<vector<int>> res;        sort(nums.begin(), nums.end());                for (int k = 0; k < nums.size(); k++) {            int rest = -nums[k];            for (int i = k + 1, j = nums.size() - 1; i < j; ) {                int sum = nums[i] + nums[j];                if (sum == rest) {                    res.push_back({nums[k], nums[i], nums[j]});                    for (int dup = nums[i]; i < j && nums[i] == dup; i++);                    for (int dup = nums[j]; i < j && nums[j] == dup; j--);                } else if (sum < rest)                    i++;                else                    j--;            }            for (int dup = nums[k]; k + 1 < nums.size() && nums[k + 1] == dup; k++);        }                return res;    }