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ProblemGiven the root of a binary tree, calculate the vertical order traversal of the binary tree.For each node at position (row, col), its left and right children will be at positions (row + 1, col - 1) and (row + 1, col + 1) respectively. The root of t

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ProblemGiven a non-empty special binary tree consisting of nodes with the non-negative value, where each node in this tree has exactly two or zero sub-node. If the node has two sub-nodes, then this node’s value is the smaller value among its two sub-nodes

ProblemGiven a chemical formula (given as a string), return the count of each atom.The atomic element always starts with an uppercase character, then zero or more lowercase letters, representing the name.One or more digits representing that element’s co

Problem输入一个字符串，打印出该字符串中字符的所有排列。你可以以任意顺序返回这个字符串数组，但里面不能有重复元素。限制：1 <= s 的长度 <= 8Example输入：s = “abc”输出：[“abc”,“acb”,“bac”,“bca”,“cab”,“cba”]Solutionclass Solution {public: vector<string> permutation(string s) { vector<

ProblemGiven an array of strings arr. String s is a concatenation of a sub-sequence of arr which have unique characters.Return the maximum possible length of s.

ProblemYou are given an integer array jobs, where jobs[i] is the amount of time it takes to complete the ith job.There are k workers that you can assign jobs to. Each job should be assigned to exactly one worker. The working time of a worker is the sum o

ProblemYou are given a data structure of employee information, which includes the employee’s unique id, their importance value and their direct subordinates’ id.For example, employee 1 is the leader of employee 2, and employee 2 is the leader of employee

ProblemGiven an integer array nums that may contain duplicates, return all possible subsets (the power set).The solution set must not contain duplicate subsets. Return the solution in any order.Constraints:1 <= nums.length <= 10-10 <= nums[i

ProblemGiven a string s, partition s such that every substring of the partition is a palindrome. Return all possible palindrome partitioning of s.A palindrome string is a string that reads the same backward as forward.Constraints:1 <= s.length <

ProblemGiven an encoded string, return its decoded string.The encoding rule is: k[encoded_string], where the encoded_string inside the square brackets is being repeated exactly k times. Note that k is guaranteed to be a positive integer.You may assume t

ProblemGiven a binary tree and a sum, find all root-to-leaf paths where each path’s sum equals the given sum.Note: A leaf is a node with no children.ExampleGiven the below binary tree and sum = 22,Return:Solution/** * Definition for a binary tree

ProblemGiven a binary tree, return all root-to-leaf paths.Note: A leaf is a node with no children.ExampleSolution/** * Definition for a binary tree node. * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * Tree

ProblemThere are N rooms and you start in room 0. Each room has a distinct number in 0, 1, 2, …, N-1, and each room may have some keys to access the next room.Formally, each room i has a list of keys rooms[i], and each key rooms[i][j] is an integer in [

ProblemGiven a list of airline tickets represented by pairs of departure and arrival airports [from, to], reconstruct the itinerary in order. All of the tickets belong to a man who departs from JFK. Thus, the itinerary must begin with JFK.Note:If there

ProblemGiven a string containing digits from 2-9 inclusive, return all possible letter combinations that the number could represent.A mapping of digit to letters (just like on the telephone buttons) is given below. Note that 1 does not map to any letters

ProblemGiven an integer array, your task is to find all the different possible increasing subsequences of the given array, and the length of an increasing subsequence should be at least 2.Constraints:The length of the given array will not exceed 15.Th

ProblemYou have 4 cards each containing a number from 1 to 9. You need to judge whether they could operated through *, /, +, -, (, ) to get the value of 24.Note:The division operator / represents real division, not integer division. For example, 4 / (1

ProblemYou are given a 2D char matrix representing the game board. ‘M’ represents an unrevealed mine, ‘E’ represents an unrevealed empty square, ‘B’ represents a revealed blank square that has no adjacent (above, below, left, right, and all 4 diagonals) m

ProblemAn image is represented by a 2-D array of integers, each integer representing the pixel value of the image (from 0 to 65535).Given a coordinate (sr, sc) representing the starting pixel (row and column) of the flood fill, and a pixel value newColor

ProblemGiven a 2D board containing ‘X’ and ‘O’ (the letter O), capture all regions surrounded by ‘X’.A region is captured by flipping all 'O’s into 'X’s in that surrounded region.ExampleSolution从边缘的O开始，进行DFS，找到所有相连的O。然后将所有没有跟边缘的O相连的O标记成X。class Solut

ProblemGiven a string containing only digits, restore it by returning all possible valid IP address combinations.A valid IP address consists of exactly four integers (each integer is between 0 and 255) separated by single points.ExampleInput: “2552551

ProblemThe thief has found himself a new place for his thievery again. There is only one entrance to this area, called the “root.” Besides the root, each house has one and only one parent house. After a tour, the smart thief realized that “all houses in t

ProblemThere are a total of numCourses courses you have to take, labeled from 0 to numCourses-1.Some courses may have prerequisites, for example to take course 0 you have to first take course 1, which is expressed as a pair: [0,1]Given the total number

ProblemGiven an integer matrix, find the length of the longest increasing path.From each cell, you can either move to four directions: left, right, up or down. You may NOT move diagonally or move outside of the boundary (i.e. wrap-around is not allowed).

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You are given two jugs with capacities x and y litres. There is an infinite amount of water supply available. You need to determine whether it is possible to measure exactly z litres using these two j...

ProblemGiven a non-empty 2D array grid of 0’s and 1’s, an island is a group of 1’s (representing land) connected 4-directionally (horizontal or vertical.) You may assume all four edges of the grid ar...

ProblemGiven a binary tree, return the sum of values of nodes with even-valued grandparent. (A grandparent of a node is the parent of its parent, if it exists.)If there are no nodes with an even-va...

ProblemYou are given a binary tree in which each node contains an integer value (which might be positive or negative). Design an algorithm to count the number of paths that sum to a given value. The ...