973.py

'''
Given an array of points where points[i] = [xi, yi] 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 <= xi, yi <= 104
'''

# https://leetcode.com/problems/k-closest-points-to-origin/

import unittest

def k_closest_points_to_origin(points, k):
    return sorted(points, key=lambda x: x[0] ** 2 + x[1] ** 2)[:k]

class TestKClosestPointsToOrigin(unittest.TestCase):
    def test_example1(self):
        points = [[1, 3], [-2, 2]]
        k = 1
        expected = [[-2, 2]]
        result = k_closest_points_to_origin(points, k)
        self.assertEqual(result, expected)

    def test_example2(self):
        points = [[3, 3], [5, -1], [-2, 4]]
        k = 2
        expected = [[3, 3], [-2, 4]]
        result = k_closest_points_to_origin(points, k)
        self.assertEqual(result, expected)

if __name__ == '__main__':
    unittest.main()