LeetCode 658. Find K Closest Elements 二分+双指针

Given a sorted integer array arr, two integers k and x, return the k closest integers to x in the array. The result should also be sorted in ascending order.

An integer a is closer to x than an integer b if:

• |a - x| < |b - x|, or
• |a - x| == |b - x| and a < b

Solution

先用二分确定 x 的位置，然后用双指针来确定左右范围

点击查看代码

class Solution:
    def findClosestElements(self, arr: List[int], k: int, x: int) -> List[int]:
        def left_bound(arr, x):
            left = 0
            right = len(arr)
 
            while left<right:
                mid = left+int((right-left)/2)
                if arr[mid]==x:
                    right=mid
                elif arr[mid]<x:
                    left=mid+1
                elif arr[mid]>x:
                    right=mid
            return left
        
        right = left_bound(arr,x)
        left = right-1
        print(right, left)
 
        for _ in range(k):
            if left<0: 
                right+=1
            elif right>=len(arr):
                left-=1
            else:
                if x-arr[left]<=arr[right]-x:
                    left-=1
                else:
                    right+=1
        return arr[left+1:right]