leetcode-973-最接近原点的K个点

题目描述：

 

 

 

 可参考：题215

方法一：排序

class Solution:
    def kClosest(self, points: List[List[int]], K: int) -> List[List[int]]:
        points.sort(key = lambda P: P[0]**2 + P[1]**2)
        return points[:K]

快排+分治：

class Solution:
    def kClosest(self, points: List[List[int]], K: int) -> List[List[int]]:
        # 计算欧几里得距离
        distance = lambda i: points[i][0] ** 2 + points[i][1] ** 2
        
        def work(i, j, K):
            if i > j:
                return
            # 记录初始值
            oi, oj = i, j
            # 取最左边为哨兵值
            pivot = distance(oi)
            while i != j:
                while i < j and distance(j) >= pivot:
                    j -= 1
                while i < j and distance(i) <= pivot:
                    i += 1
                if i < j:
                    # 交换值
                    points[i], points[j] = points[j], points[i] 
                
            # 交换哨兵
            points[i], points[oi] = points[oi], points[i]
            
            # 递归
            if K <= i - oi + 1:
                # 左半边排序
                work(oi, i - 1, K)
            else:
                # 右半边排序
                work(i + 1, oj, K - (i - oi + 1))
                
        work(0, len(points) - 1, K)
        return points[:K]

方法三：堆排序

from heapq import heappush, heappop 

class Solution:
    def kClosest(self, points: List[List[int]], K: int) -> List[List[int]]:
        queue = []
        distance = lambda x: points[x][0]**2 + points[x][1]**2
        length = len(points)
        for i in range(length):
            heappush(queue, (distance(i), points[i]))
        res = []
        for i in range(K):
            res.append(heappop(queue)[1])
        return res