String | K5kC

Minimum Remove to Make Valid Parentheses

Serialize and Deserialize N-Ary Tree

Longest Happy String Problem

Open the Lock Problem

Partition Labels Problem

Encode and Decode TinyURL Problem

Unique Length-3 Palindromic Subsequences

Decode String Problem

Frequency of the Most Frequent Element

Minimum Number of Swaps to Make the String Balanced Problem