leetcode/algorithms/cpp/3Sum/3Sum.cpp at main · MichelleZ/leetcode · GitHub

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// Source: https://leetcode.com/problems/3sum/
// Author: Miao Zhang
// Date:   2021-01-05

class Solution {
public:
    vector<vector<int>> threeSum(vector<int>& nums) {
        sort(nums.begin(), nums.end());
        vector<vector<int>> res;
        int n = nums.size();
        for (int i = 0; i < n - 2; i++) {
            if (i > 0 && nums[i - 1] == nums[i]) continue;
            int target = -1 * nums[i];
            int l = i + 1;
            int r = n - 1;
            while (l < r) {
                if (nums[l] + nums[r] == target) {
                    vector<int> tmp;
                    tmp.push_back(nums[i]);
                    tmp.push_back(nums[l]);
                    tmp.push_back(nums[r]);
                    res.push_back(tmp);
                    l++;
                    while (l < r && nums[l] == nums[l - 1]) l++;
                } else if (nums[l] + nums[r] < target) {
                    l++;
                } else {
                    r--;
                }
            }
        }
        return res;
    }
};