15_3Sum.cpp

#include <bits/stdc++.h>
using namespace std;

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