15 三数之和

https://leetcode.cn/leetbook/read/top-interview-questions-medium/xvpj16/

cost: 26m42s

class Solution {
public:
    vector<vector<int>> threeSum(vector<int>& nums) {
        vector<vector<int>> res;
        std::sort(nums.begin(), nums.end());
        for (int i = 0; i < nums.size(); i++) {
            if (i > 0 && nums[i] == nums[i - 1]) {
                continue;
            }
            if (nums[i] > 0) {
                break;
            }
            int target = -nums[i];
            for (int j = i + 1, k = nums.size() - 1; j < k;) {
                int sum = nums[j] + nums[k];
                if (sum < target) {
                    j++;
                    continue;
                }
                if (sum > target) {
                    k--;
                    continue;
                }
                if (j > i + 1 && nums[j] == nums[j - 1]) {
                    j++;
                    continue;
                }
                if (k < nums.size() - 1 && nums[k] == nums[k + 1]) {
                    k--;
                    continue;
                }
                res.push_back({nums[i], nums[j], nums[k]});
                j++;
                k--;
            }
        }
        return res;
    }
};