dongbeier的博客

You need to find the largest value in each row of a binary tree.Example:Input: 1 / \ 3 2 / \ \ 5 3 9 Output: [1, 3, 9] 这道题让我们找二叉树每行的最大的结点值，那么实际上最直...

Given two words (beginWord and endWord), and a dictionary's word list, find the length of shortest transformation sequence from beginWord to endWord, such that:Only one letter can be changed at a time...

Given an array nums of n integers where n > 1,  return an array output such that output[i] is equal to the product of all the elements of nums except nums[i].Example:Input: [1,2,3,4] Output: [24,1...

Given a binary tree, find its maximum depth.The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.Note: A leaf is a node with no children.Ex...

Given a string S and a string T, find the minimum window in S which will contain all the characters in T in complexity O(n).Example:Input: S = "ADOBECODEBANC", T = "ABC" Output: "BANC" Note:If there i...

Given a collection of distinct integers, return all possible permutations.Example:Input: [1,2,3] Output: [ [1,2,3], [1,3,2], [2,1,3], [2,3,1], [3,1,2], [3,2,1] ] 函数  next_permutation()/** ...

Suppose an array sorted in ascending order is rotated at some pivot unknown to you beforehand.(i.e., [0,1,2,4,5,6,7] might become [4,5,6,7,0,1,2]).You are given a target value to search. If found in t...

Given a list of sorted characters letters containing only lowercase letters, and given a target letter target, find the smallest element in the list that is larger than the given target.Letters also w...

Given two sparse matrices A and B, return the result of AB.You may assume that A's column number is equal to B's row number.Example:A = [ [ 1, 0, 0], [-1, 0, 3] ] B = [ [ 7, 0, 0 ], [ 0, 0, 0...

Evaluate the value of an arithmetic expression in Reverse Polish Notation.Valid operators are +, -, *, /. Each operand may be an integer or another expression.Note:Division between two integers should...

In the "100 game," two players take turns adding, to a running total, any integer from 1..10. The player who first causes the running total to reach or exceed 100 wins.What if we change the game so th...

Given a set of non-overlapping intervals, insert a new interval into the intervals (merge if necessary).You may assume that the intervals were initially sorted according to their start times.Example 1...

Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).For example, this binary tree [1,2,2,3,4,4,3] is symmetric: 1 / \ 2 2 / \ / \ 3 4 4 3 But the...

Given a string, your task is to count how many palindromic substrings in this string.The substrings with different start indexes or end indexes are counted as different substrings even they consist of...

Given a positive integer num, write a function which returns True if num is a perfect square else False.Note: Do not use any built-in library function such as sqrt.Example 1:Input: 16 Returns: True Ex...

Given a string S, find the number of different non-empty palindromic subsequences in S, and return that number modulo 10^9 + 7.A subsequence of a string S is obtained by deleting 0 or more characters ...

Given a non-negative integer c, your task is to decide whether there're two integers a and b such that a2 + b2= c.Example 1:Input: 5 Output: True Explanation: 1 * 1 + 2 * 2 = 5 Example 2:Input: 3 Outp...

Given 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 va...

Given a collection of numbers that might contain duplicates, return all possible unique permutations.Example:Input: [1,1,2] Output: [ [1,1,2], [1,2,1], [2,1,1] ] 重新实现next_permutation()/** * * ...

mplement an iterator over a binary search tree (BST). Your iterator will be initialized with the root node of a BST.Calling next() will return the next smallest number in the BST.Note: next() and hasN...

Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.Example:Input: 1->2->4, 1->3->4 Output: 1->1...

Merge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity.Example:Input: [   1->4->5,   1->3->4,   2->6 ] Output: 1->1->2->3->4->4...

You are a professional robber planning to rob houses along a street. Each house has a certain amount of money stashed, the only constraint stopping you from robbing each of them is that adjacent house...

Given a binary tree, return the zigzag level order traversal of its nodes' values. (ie, from left to right, then right to left for the next level and alternate between).For example:Given binary tree [...

Given an array of integers, return indices of the two numbers such that they add up to a specific target.You may assume that each input would have exactly one solution, and you may not use the same el...

Given an array of integers nums sorted in ascending order, find the starting and ending position of a given target value.Your algorithm's runtime complexity must be in the order of O(log n).If the tar...

Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree.According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between two nodes v an...

Given an array of integers nums and a positive integer k, find whether it's possible to divide this array into knon-empty subsets whose sums are all equal.Example 1:Input: nums = [4, 3, 2, 3, 5, 2, 1]...

This is a follow up of Shortest Word Distance. The only difference is now word1 could be the same as word2.Given a list of words and two words word1 and word2, return the shortest distance between the...

Numbers can be regarded as product of its factors. For example,8 = 2 x 2 x 2; = 2 x 4. Write a function that takes an integer n and return all possible combinations of its factors.Note: Each combina...

Given a binary tree, find all leaves and then remove those leaves. Then repeat the previous steps until the tree is empty.Example:Given binary tree  1 / \ 2 3 / \ ...

Design a max stack that supports push, pop, top, peekMax and popMax. push(x) -- Push element x onto stack.pop() -- Remove the element on top of the stack and return it.top() -- Get the element on the ...

Given a binary tree where all the right nodes are either leaf nodes with a sibling (a left node that shares the same parent node) or empty, flip it upside down and turn it into a tree where the origin...

There are a row of n houses, each house can be painted with one of the three colors: red, blue or green. The cost of painting each house with a certain color is different. You have to paint all the ho...

Design and implement a TwoSum class. It should support the following operations:add and find.add - Add the number to an internal data structure.find - Find if there exists any pair of numbers which su...

Given a nested list of integers, return the sum of all integers in the list weighted by their depth.Each element is either an integer, or a list -- whose elements may also be integers or other lists.D...

This is a follow up of Shortest Word Distance. The only difference is now you are given the list of words and your method will be called repeatedly many times with different parameters. How would you ...

Given two strings s and t, determine if they are isomorphic.Two strings are isomorphic if the characters in s can be replaced to get t.All occurrences of a character must be replaced with another char...

Given an integer array nums, find the contiguous subarray (containing at least one number) which has the largest sum and return its sum.Example:Input: [-2,1,-3,4,-1,2,1,-5,4], Output: 6 Explanation: [...

Serialization is the process of converting a data structure or object into a sequence of bits so that it can be stored in a file or memory buffer, or transmitted across a network connection link to be...