973. K Closest Points to Origin

Problem Statement

Medium

Given an array of points where points[i] = [x_i, y_i] represents a point on the X-Y plane and an integer k, return the k closest points to the origin (0, 0).

The distance between two points on the X-Y plane is the Euclidean distance (i.e., √(x₁ - x₂)² + (y₁ - y₂)²).

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]]
Explanation: The answer [[-2,4],[3,3]] would also be accepted.

Constraints:

1 <= k <= points.length <= 10⁴
-10⁴ < x_i, y_i < 10⁴

C++

Source file

class Solution {
    
public:
    vector<vector<int>> kClosest(vector<vector<int>>& points, int k) {
        vector <vector<int>> dist, res;
        for (int i=0; i<points.size(); i++){
            dist.push_back({points[i][0]*points[i][0] + points[i][1]*points[i][1], i});
        }
        sort(dist.begin(), dist.end());
        for (int i=0; i<k; i++){
            res.push_back(points[dist[i][1]]);
            cout << points[dist[i][1]][0] << " " << points[dist[i][1]][1];
        }
        return res;
    }
};