CodingHardcod-g156

Subject PalindromesLevel Senior–Staff~35 minCommon in Algorithms & data structures interviewsIndustries Software development

Question

Return the minimum number of characters you must insert anywhere into s to make it a palindrome. For example "mbadm" needs 2 insertions (one valid result is "mdbabdm"), while "zzazz" is already a palindrome and needs 0. The empty string and single characters need 0. Strings can be up to ~1000 characters; an O(n^2) DP is expected.

Implement

min_insertions_palindrome(s: str) → int

Examples

in["mbadm"]out2

What a strong answer looks like

State your approach and its time/space complexity out loud before you optimize. Handle the edge cases (empty input, duplicates, overflow), and say why you chose this over the brute force. Green tests are the floor, not the grade.

Learn the concepts

Vibe coding: describe the solution in plain language (or narrate it) and the coach grades your approach. Generating runnable code from your description is coming next.

Run or narrate your approach, then ask the coach.