Given two integers a and b, return any string s such that: s has length a + b and contains exactly a ‘a’ letters, and exactly b ‘b’ letters, The substring ‘aaa’ does not occur in s, and The substring

A string s is called happy if it satisfies the following conditions: s only contains the letters ‘a’, ‘b’, and ‘c’. s does not contain any of “aaa”, “bbb”, or “ccc” as a substring. s contains at most

You are given an array of characters letters that is sorted in non-decreasing order, and a character target. There are at least two different characters in letters. Return the smallest character in le

Given a non-negative integer c, decide whether there’re two integers a and b such that a2 + b2 = c. Example 1:Input: c = 5Output: trueExplanation: 1 * 1 + 2 * 2 = 5 Example 2:Input: c &

Given a binary tree where node values are digits from 1 to 9. A path in the binary tree is said to be pseudo-palindromic if at least one permutation of the node values in the path is a palindrome. Ret

A parentheses string is valid if and only if: It is the empty string, It can be written as AB (A concatenated with B), where A and B are valid strings, or It can be written as (A), where A is a valid

You are given two linked lists: list1 and list2 of sizes n and m respectively. Remove list1’s nodes from the ath node to the bth node, and put list2 in their place. The blue edges and nodes in the fol

A binary tree is named Even-Odd if it meets the following conditions:The root of the binary tree is at level index 0, its children are at level index 1, their children are at level index 2, etc.For ev

Given a binary tree root and an integer target, delete all the leaf nodes with value target. Note that once you delete a leaf node with value target, if its parent node becomes a leaf node and has the

Given the root of a binary tree, return the same tree where every subtree (of the given tree) not containing a 1 has been removed. A subtree of a node node is node plus every node that is a descendant