Robina Li

Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree.

Design a data structure that supports adding new words and finding if a string matches any previously added string.

There is a restaurant with a single chef. You are given an array customers, where customers[i] = [arrival_i, time_i]:

You have a set of integers s, which originally contains all the numbers from 1 to n. Unfortunately, due to some error, one of the numbers in s got duplicated...

Given a string s which consists of lowercase or uppercase letters, return the length of the longest palindrome that can be built with those letters.

Given a string s, find the first non-repeating character in it and return its index. If it does not exist, return -1.

Given two integer arrays nums1 and nums2, return an array of their intersection. Each element in the result must be unique and you may return the result in any order....

Given the root of a binary tree, invert the tree, and return its root.

You are given an array of strings words and a string pref.

Given a string s, return the length of the longest substring between two equal characters, excluding the two equal characters themselves. If no such substring exists, return -1.