LeetCode 34: Find First and Last Position of Element in Sorted Array ACERS Guide
Subtitle / Summary This problem is the standard upgrade from “find one target” to “find the whole target block.” The clean solution is not a special-case binary search, but two boundary searches: lower bound for the start and upper bound for the end. Reading time: 12-14 min Tags: binary search, lower bound, upper bound, range query SEO keywords: Search Range, lower bound, upper bound, LeetCode 34 Meta description: Use lower-bound and upper-bound binary search to find the first and last positions of a target in a sorted array, with pitfalls, engineering scenarios, and runnable implementations in six languages. Target Readers Learners who already know basic binary search but struggle with boundary problems Engineers who query sorted logs, timestamps, or grouped IDs Interview candidates who want one reusable range-search template Background / Motivation Finding a single target in a sorted array is the easy version. Real systems often need the full range: ...