Robina Li

In this problem, a rooted tree is a directed graph such that there is exactly one node (the root) for which all other nodes are descendants of this node, plus...

Given the root of a binary search tree (BST) and a node p in it, return the in-order successor of that node in the BST. If the given node has...

Given a binary array nums, return the maximum number of consecutive 1’s in the array if you can flip at most one 0.

An image smoother is a filter of the size 3 x 3 that can be applied to each cell of an image by rounding down the average of the cell...

You are given a string s and an array of strings words. You should add a closed pair of bold tag <b> and </b> to wrap the substrings in s...

Given a time represented in the format "HH:MM", form the next closest time by reusing the current digits. There is no limit on how many times a digit can be...

You have n bulbs in a row numbered from 1 to n. Initially, all the bulbs are turned off. On day i (for i from 0 to n-1), we turn...

Given two strings a and b, return the minimum number of times you should repeat string a so that string b is a substring of it. If it is impossible...

In this problem, a tree is an undirected graph that is connected and has no cycles.

You are in a city that consists of n intersections numbered from 0 to n - 1 with bi-directional roads between some intersections. The inputs are generated such that you...