Leetcode: K Closest Points to Origin

K Closest Points to Origin



Similar Problems:


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.)

Note:

  1. 1 <= K <= points.length <= 10000
  2. -10000 < points[i][0] < 10000
  3. -10000 < points[i][1] < 10000

Github: code.dennyzhang.com

Credits To: leetcode.com

Leave me comments, if you have better ways to solve.


// Blog link: https://code.dennyzhang.com/k-closest-points-to-origin
// Basic Idea: sort
// Complexity: Time O(n*log(n)), Space O(n)
import "sort"
type Point struct {
    i int
    v int
}
func kClosest(points [][]int, K int) [][]int {
    l := []Point{}
    for i, p := range points {
        l = append(l, Point{i, p[0]*p[0]+p[1]*p[1]})
    }
    sort.Slice(l, func(i, j int) bool {
      return l[i].v < l[j].v
    })

    res := [][]int{}
    for i := K-1; i>=0; i-- {
        res = append(res, points[l[i].i])
    }
    return res
}
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