30. K Closest Points to Origin.cpp

/*

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.)

*/

#include<cmath>

class Solution {
public:
    vector<vector<int>> kClosest(vector<vector<int>>& points, int K) 
    {
        multimap<double,int>mp;
        vector<vector<int>>result;
        
        for(int i=0;i<points.size();i++)
        {
            double dist = sqrt( ( points[i][0]*points[i][0] ) + ( points[i][1]*points[i][1] ) );
            mp.insert({dist,i});
        }
        
        int loop=0;
        for(auto x:mp)
        {
            if(loop==K)
                break;
            result.push_back(points[x.second]);
            loop++;
        }
    return result;
    }
};