Remove Duplicates In-Place | LeetCode 26 Two-Pointer Explained Step by Step
Remove duplicates from a sorted array in-place — no extra space, no tricks, just clean two-pointer logic.
LeetCode 26 broken down with a full diagram walkthrough, pseudocode, and a working Python solution.
0:00 Problem Overview
1:00 Approach & Algorithm
2:00 Pseudocode
3:00 Diagram Walkthrough
5:00 Code Solution
6:00 Runtime & Outro
We use a k-pointer to track the boundary of unique elements while i scans forward through the array. When nums[i] differs from nums[k], we advance k and overwrite — that's the whole pattern. O(n) time, O(1) space. Once you see it drawn out, it clicks immediately. This is a foundational two-pointer problem that shows up in FAANG interviews and feeds directly into harder sorted-array problems — understand it here, and the harder variants become much easier to pattern-match.
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