973 - K Closest Points to Origin

2020/05/30

leetcode

Problem

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.)

Solution

Solution 1: sort

class Solution:
    def kClosest(self, points, K: int):
        return sorted(points, key=lambda p: p[0]**2 + p[1]**2)[:K]

Solution 2: heap

class Solution:
    def kClosest(self, points, K):
        return heapq.nsmallest(K, points, lambda (x, y): x * x + y * y)