LeetCode15. 三数之和

class Solution { public: vector<vector<int>> threeSum(vector<int>& nums) { vector<vector<int>> ans; int n = nums.size(); if (n < 3) { return ans; } sort(nums.begin(), nums.end()); for (int first = 0; first < n - 2; first++) { if (nums[first] > 0) { return ans; } if (first > 0 && nums[first] == nums[first - 1]) { continue; } int second = first + 1, third = n - 1; while (second < third) { if (second > first + 1 && nums[second] == nums[second - 1]) { second++; continue; } if (nums[first] + nums[second] + nums[third] == 0) { ans.push_back({ nums[first], nums[second], nums[third] }); second++; third--; } else if (nums[first] + nums[second] + nums[third] > 0) { third--; } else if (nums[first] + nums[second] + nums[third] < 0) { second++; } } } return ans; } };