力扣15. 三数之和（非哈希版）

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