LeetCode 973. K Closest Points to Origin

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题目

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:

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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:

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

思路

TopK问题.
使用小根堆，用每个元素距离原点的距离和该坐标组成tuple放到list里，会按照第一个元素自动排序。
nsmallest可以直接取出最小的K个tuple.

代码

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class Solution(object):
    def kClosest(self, points, K):
        """
        :type points: List[List[int]]
        :type K: int
        :rtype: List[List[int]]
        """
        dis = []
        for p in points:
            d = math.sqrt(p[0]*p[0]+p[1]*p[1])
            dis.append((d, p))
        heapq.heapify(dis)
        return [d[1] for d in heapq.nsmallest(K, dis)]