Is Longest Common Prefix After at Most One Removal easy or hard?

The problem is typically classified as Medium difficulty. The main challenge is recognizing that only the first mismatch matters and that you can simulate the allowed removal using two pointer branches instead of rebuilding strings.

Longest Common Prefix After at Most One Removal Python/Java solution

Most implementations follow the same logic across languages. Maintain two indices for the strings and track the first mismatch. After a mismatch, check both skip possibilities and compute the resulting prefix length. The algorithm translates directly to Python, Java, C++, Go, or JavaScript.

How to solve Longest Common Prefix After at Most One Removal in O(n)?

Use two pointers to scan both strings from left to right. When characters match, advance both pointers. When the first mismatch occurs, evaluate two scenarios: skip the character in the first string or skip the character in the second string. Continue matching from those positions and take the maximum prefix length.

What is the best approach for Longest Common Prefix After at Most One Removal?

The most efficient approach uses the two pointers technique. Traverse both strings together and stop at the first mismatch. At that point, simulate the single allowed removal by skipping a character in either string and continue matching. This runs in O(n) time with O(1) extra space.

Is Longest Common Prefix After at Most One Removal asked at Google/Amazon/Meta?

String comparison problems with limited edits are common in interviews at companies like Google, Amazon, and Meta. Variations appear in problems involving edit distance, prefix matching, or two‑pointer string validation. The pattern of handling a single allowed modification is frequently tested.

What data structure is used in Longest Common Prefix After at Most One Removal?

The solution mainly relies on basic string traversal with the two pointers technique. No advanced data structures are needed. The algorithm compares characters directly using indices while allowing one conditional skip.

What is the time complexity of Longest Common Prefix After at Most One Removal?

The optimal solution runs in O(n) time where n is the length of the shorter string. Each character is processed at most once while scanning both strings with two pointers. Space complexity remains O(1) because no additional data structures are required.

Description Hints 1 Solution

3460. Longest Common Prefix After at Most One Removal

Medium68.3% acceptancePremium elsewhere, free here

You are given two strings s and t.

Return the length of the longest common prefix between s and t after removing at most one character from s.

Note: s can be left without any removal.

Example 1:

Input: s = "madxa", t = "madam"

Output: 4

Explanation:

Removing s[3] from s results in "mada", which has a longest common prefix of length 4 with t.

Example 2:

Input: s = "leetcode", t = "eetcode"

Output: 7

Explanation:

Removing s[0] from s results in "eetcode", which matches t.

Example 3:

Input: s = "one", t = "one"

Output: 3

Explanation:

No removal is needed.

Example 4:

Input: s = "a", t = "b"

Output: 0

Explanation:

s and t cannot have a common prefix.

Constraints:

1 <= s.length <= 10⁵
1 <= t.length <= 10⁵
s and t contain only lowercase English letters.

Topics

String Two Pointers

Hints open one at a time

Hint 1

Maintain pointers to the beginning of both strings and remove the first position where they differ in s (if any).

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3460. Longest Common Prefix After at Most One Removal

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Hints open one at a time

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