A Lesson from a Naive Binary Search

tabularasa8931@gmail.com (Han) — Mon, 30 Jun 2025 00:00:00 +0000

A Lesson from a Naive Binary Search

I’ve been grinding hard every day, solving coding problems to get better at algorithms. Recently, I came across something interesting—a naive implementation of binary search can actually cause a bug. It’s a small detail, but it matters.

 
 
 
 
def binary_search(nums, target):
 left, right = 0, len(nums) - 1
 while left <= right:
 mid = (left + right) // 2
 if nums[mid] == target:
 return mid
 elif nums[mid] < target:
 left = mid + 1
 else:
 right = mid - 1
 return -1

It works fine in Python—but I recently learned that the way I calculate mid can cause problems in some cases.

Algorithm on Han's XYZ

A Lesson from a Naive Binary Search

A Lesson from a Naive Binary Search