Day30. KClosestPointsToOrigin.cpp

/*

K Closest Points to Origin

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.)

 

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.)
 

Note:

1. 1 <= K <= points.length <= 10000
2. -10000 < points[i][0] < 10000
3. -10000 < points[i][1] < 10000

*/

class Solution {
public:
    vector<vector<int>> kClosest(vector<vector<int>>& points, int K) 
    {
        int n=points.size();
        vector<pair<long,int>>v (n);
        vector<vector<int>> sol;
        for(int i=0;i<n;i++)
        {
            long l= pow(points[i][0],2) + pow(points[i][1],2);
            v[i]={l,i};
        }
        sort(v.begin(),v.end());
        for(int i=0;i<K;i++)
        {
            sol.push_back(points[v[i].second]);
        }
        return sol;
    }
};