LeetCode/15_c.cpp at master · changqing18/LeetCode · GitHub

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#include <algorithm>
#include <vector>
using namespace std;
//不一定比我写的快
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++)
    {

        int target = -nums[i];
        int front = i + 1;
        int back = nums.size() - 1;

        if (target < 0)
        {
            break;
        }

        while (front < back)
        {

            int sum = nums[front] + nums[back];

            // Finding answer which start from number nums[i]
            if (sum < target)
                front++;

            else if (sum > target)
                back--;

            else
            {
                vector<int> triplet(3, 0);
                triplet[0] = nums[i];
                triplet[1] = nums[front];
                triplet[2] = nums[back];
                res.push_back(triplet);

                // Processing duplicates of Number 2
                // Rolling the front pointer to the next different number forwards
                while (front < back && nums[front] == triplet[1])
                    front++;

                // Processing duplicates of Number 3
                // Rolling the back pointer to the next different number backwards
                while (front < back && nums[back] == triplet[2])
                    back--;
            }
        }

        // Processing duplicates of Number 1
        while (i + 1 < nums.size() && nums[i + 1] == nums[i])
            i++;
    }

    return res;
}