973. K Closest Points to Origin

1. Description

We have a list of points on the plane. Find the K closest points to the origin (0, 0).
(Here, the distance between two points on a plane is the Euclidean distance.)
You may return the answer in any order. The answer is guaranteed to be unique (except for the order that it is in.)

2. Example

Example 1:
Input: points = [[1,3],[-2,2]], K = 1
Output: [[-2,2]]
Explanation:
The distance between (1, 3) and the origin is sqrt(10).
The distance between (-2, 2) and the origin is sqrt(8).
Since sqrt(8) < sqrt(10), (-2, 2) is closer to the origin.
We only want the closest K = 1 points from the origin, so the answer is just [[-2,2]].

Example 2:
Input: points = [[3,3],[5,-1],[-2,4]], K = 2
Output: [[3,3],[-2,4]]
(The answer [[-2,4],[3,3]] would also be accepted.)

3. Note

• 1 <= K <= points.length <= 10000
• -10000 < points[i][0] < 10000
• -10000 < points[i][1] < 10000

4. Solutions

My Accepted Solution

n = m_points.size()
Time complexity: O($nlog_2k$)
Space complexity: O(1)

class Solution 
{
public:
    //vector<vector<int>> kClosest(vector<vector<int>>& points, int K)
    vector<vector<int>> kClosest(vector<vector<int>> &m_points, int k) 
    {
        partial_sort(m_points.begin(), m_points.begin()+k, m_points.end(), [](vector<int> left, vector<int> right){return pow(left.front(),2)+pow(left.back(),2) < pow(right.front(),2)+pow(right.back(),2);});
        m_points.resize(k);
        return m_points;
    }
};