# Find K Closest Points to the Origin in C++

C++Server Side ProgrammingProgramming

Suppose we have a set of points. Our task is to find K points which are closest to the origin. Suppose the points are (3, 3), (5, -1) and (-2, 4). Then the closest two (K = 2) points are (3, 3), (-2, 4).

To solve this problem, we will sort the list of points based on their Euclidean distance, after that take the top most K elements from the sorted list. Those are the K nearest points.

## Example

Live Demo

#include<iostream>
#include<algorithm>
using namespace std;
class Point{
private:
int x, y;
public:
Point(int x = 0, int y = 0){
this->x = x;
this->y = y;
}
void display(){
cout << "("<<x<<", "<<y<<")";
}
friend bool comparePoints(Point &p1, Point &p2);
};
bool comparePoints(Point &p1, Point &p2){
float dist1 = (p1.x * p1.x) + (p1.y * p1.y);
float dist2 = (p2.x * p2.x) + (p2.y * p2.y);
return dist1 < dist2;
}
void closestKPoints(Point points[], int n, int k){
sort(points, points+n, comparePoints);
for(int i = 0; i<k; i++){
points[i].display();
cout << endl;
}
}
int main() {
Point points[] = {{3, 3},{5, -1},{-2, 4}};
int n = sizeof(points)/sizeof(points[0]);
int k = 2;
closestKPoints(points, n, k);
}

## Output

(3, 3)
(-2, 4)
Published on 22-Oct-2019 07:02:41