A robot is located at the top-left corner of a m x n grid (marked 'Start' in the diagram below).The robot can only move either down or right at any point in time. The robot is trying to reach the

Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum.For example:Given the below binary tree and sum

Determine whether an integer is a palindrome. Do this without extra space.click to show spoilers.Some hints:Could negative integers be palindromes? (ie, -1)If you are thinking of convertin

Given preorder and inorder traversal of a tree, construct the binary tree.Note:You may assume that duplicates do not exist in the tree.给定先序序列和中序序列建立二叉树， 递归解决， 按顺序扫描先序序列，每一次扫描的第一个节点作为根，然后在中序序

Given inorder and postorder traversal of a tree, construct the binary tree.Note:You may assume that duplicates do not exist in the tree.这个根据中序和后序建立二叉树与根据先序中序建立非常像，只需要把从先序从头开始扫描变成从后序的尾部

Given a list, rotate the list to the right by k places, where k is non-negative.For example:Given 1->2->3->4->5->NULL and k = 2,return 4->5->1->2->3->NULL.题意是说给定一个k >= 0 把链表循环右移k位， 这

Given a binary tree, determine if it is a valid binary search tree (BST).Assume a BST is defined as follows:/** * Definition for binary tree * struct TreeNode { * int val; * TreeNode *

Given a singly linked list where elements are sorted in ascending order, convert it to a height balanced BST.题目描述很简单，就是说把一个升序链表转换成平衡二叉排序树，即 最优二叉排序树， 最优二叉排序树的搜索时间为logn 即树的高度， 因为链表很难处理，直接转换成数组比较容易

Sort a linked list using insertion sort.这里给单链表进行插入排序，个人想到两种方法 一种是交换节点的指针，一种是交换节点的值，前者要判断头节点，感觉比较麻烦，就用了交换值的方法， 通常的插入排序是在插入点的位置依次与前面的元素相比较，如果比前面的小，就把当前的位置的值变成前一个位置的值，最后得到的是最终插入位置， 这里单链表没办法往前搜索，那么就从头

Given an array with n objects colored red, white or blue, sort them so that objects of the same color are adjacent, with the colors in the order red, white and blue.Here, we will use the integers 0,

Given an array of words and a length L, format the text such that each line has exactly L characters and is fully (left and right) justified.You should pack your words in a greedy approach; that i

Given a binary tree, find its minimum depth.The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node.对于给定的二叉树，求最小高度（最小高度为根节点到最近的叶子节点的

阔别了已久的leetcode 又回来了。Given a binary tree, return the preorder traversal of its nodes' values.For example:Given binary tree {1,#,2,3}, 1 \ 2 / 3return [1,2,3].

Given a binary tree, return the postorder traversal of its nodes' values.For example:Given binary tree {1,#,2,3}, 1 \ 2 / 3return [3,2,1].Note: Recursive solut

Given a non-negative number represented as an array of digits, plus one to the number.The digits are stored such that the most significant digit is at the head of the list.这个题就不说了，加法操作。。

Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.For example,"A man, a plan, a canal: Panama" is a palindrome."race a car" is not a

Given a roman numeral, convert it to an integer.Input is guaranteed to be within the range from 1 to 3999.罗马数字转成整数的题目，题目规定数字在1-3999之间，罗马数字用7个字母表示：I（1）、V（5）、X（10）、L（50）、C（100）、D（500）、M（1000） 规则

Write a function to find the longest common prefix string amongst an array of strings.求一个字符串数组中的所有字符串的最长公共前缀，这个就一个一个字符串从头比较就行了。class Solution {public: string longestCommonPrefix(vector &s

Given a m x n matrix, if an element is 0, set its entire row and column to 0. Do it in place.click to show follow up.Follow up:Did you use extra space?A straight forward solution using O(m

Given a 2D board containing 'X' and 'O', capture all regions surrounded by 'X'.A region is captured by flipping all 'O's into 'X's in that surrounded region.For example,X X X XX O O XX X

Determine if a Sudoku is valid, according to: Sudoku Puzzles - The Rules.The Sudoku board could be partially filled, where empty cells are filled with the character '.'.A partially fille

Reverse a linked list from position m to n. Do it in-place and in one-pass.For example:Given 1->2->3->4->5->NULL, m = 2 and n = 4,return 1->4->3->2->5->NULL.Note:Given m, n satisfy the fol

Given a set of distinct integers, S, return all possible subsets.Note:Elements in a subset must be in non-descending order.The solution set must not contain duplicate subsets.For example,

Given a string s consists of upper/lower-case alphabets and empty space characters ' ', return the length of last word in the string.If the last word does not exist, return 0.Note: A word is

Design and implement a data structure for Least Recently Used (LRU) cache. It should support the following operations: get and set.get(key) - Get the value (will always be positive) of the key if

Given n non-negative integers representing an elevation map where the width of each bar is 1, compute how much water it is able to trap after raining.For example, Given [0,1,0,2,1,0,1,3,2,1,2,1],

Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list.For example,Given 1->2->3->3->4->4->5, return 1->2->5.Given 1->1->1

Given a binary tree, flatten it to a linked list in-place.For example,Given 1 / \ 2 5 / \ \ 3 4 6The flattened tree should look like: 1 \

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 tr

Two elements of a binary search tree (BST) are swapped by mistake.Recover the tree without changing its structure.Note:A solution using O(n) space is pretty straight forward. Could you devise a

Given an array of non-negative integers, you are initially positioned at the first index of the array.Each element in the array represents your maximum jump length at that position.Determine i

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.两个已排序的单链表合并。 很简单 直接在原有立案表上修改就行了。/** * Definition

Given a linked list, swap every two adjacent nodes and return its head.For example,Given 1->2->3->4, you should return the list as 2->1->4->3.Your algorithm should use only constant space. Y

Given an array where elements are sorted in ascending order, convert it to a height balanced BST.题目很常规 根据一个递增的数组建立一个平衡的二叉排序树。 平衡二叉排序树的特征是根节点处于数组中间位置，子树的根节点分别是数组以中间位置分割的两部分的中间位置， 即递归性质。 所以可以利用递归来

Given an array and a value, remove all instances of that value in place and return the new length.The order of elements can be changed. It doesn't matter what you leave beyond the new length.题意是从数

Given two binary trees, write a function to check if they are equal or not.Two binary trees are considered equal if they are structurally identical and the nodes have the same value./*

Reverse digits of an integer.Example1: x = 123, return 321Example2: x = -123, return -321click to show spoilers.Have you thought about this?Here are some good questions to ask before c

Find the contiguous subarray within an array (containing at least one number) which has the largest sum.For example, given the array [−2,1,−3,4,−1,2,1,−5,4],the contiguous subarray [4,−1,2,1] ha

Given a sorted array, remove the duplicates in place such that each element appear only once and return the new length.Do not allocate extra space for another array, you must do this in place with

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./** * Definition for bina