Robina Li

There are n computers numbered 0 to n-1 connected by cables. connections[i] = [a, b] means a cable connects computers a and b. You can remove an existing cable and...

Given the head of a singly linked list, return the middle node. If there are two middle nodes, return the second middle node.

You are given a string s and an array of index pairs pairs where pairs[i] = [a, b] indicates you can swap the characters at indices a and b any...

You are given an array points where points[i] = [xi, yi] represents a point on the 2D plane. The cost to connect two points is the Manhattan distance: |xi -...

We can “shift” a string by shifting each character to its successive character (with z wrapping to a). For example, "abc" can be shifted to "bcd", …, "xyz", "yza", "zab"....

Given two strings ransomNote and magazine, return true if ransomNote can be constructed by using the letters from magazine. Each letter in magazine can only be used once.

Given two strings s and t, return true if t is an anagram of s, and false otherwise. An anagram uses the exact same characters with the exact same frequencies....

Given an integer array nums and an integer k, return true if there are two distinct indices i and j such that nums[i] == nums[j] and abs(i - j) <=...

Given an integer array nums, return true if any value appears at least twice, and false if every element is distinct.

Given the root of a binary tree and an integer targetSum, return all root-to-leaf paths where the sum of the node values equals targetSum. Each path should be returned as...