u012734829的专栏

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

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.题目意思看了好几遍才看懂  用数字（0-

Given a binary tree, determine if it is a valid binary search tree (BST).Assume a BST is defined as follows:The left subtree of a node contains only nodes with keys less than the node's key.The right

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

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 devis

Given a binary tree, return the bottom-up level order traversal of its nodes' values. (ie, from left to right, level by level from leaf to root).For example:Given binary tree {3,9,20,#,#,15,7},

You are given an n x n 2D matrix representing an image.Rotate the image by 90 degrees (clockwise).Follow up:Could you do this in-place?给一个n*n矩阵 要求将其旋转90度首先想到的是另外建一个等大的二维数组 将其按旋转后的顺序一

Follow up for "Unique Paths":Now consider if some obstacles are added to the grids. How many unique paths would there be?An obstacle and empty space is marked as 1 and 0 respectively in the

Given a binary tree, determine if it is height-balanced.For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never diffe

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.返回最小路径值 只要对左右节点进行判断即可 若左右节点都为空  则直

Given an integer, convert it to a roman numeral.Input is guaranteed to be within the range from 1 to 3999. 将阿拉伯数字转换为罗马字符 建立一个二维数组来代表转换表 代码如下：public class Solution { public String intToR

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.一开始题目没看清 以为从前面开始进行逆转 其实是从后面开始计数 使

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 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.E

The set [1,2,3,…,n] contains a total of n! unique permutations.By listing and labeling all of the permutations in order,We get the following sequence (ie, for n = 3):"123""132""213""231""3

Given a roman numeral, convert it to an integer.Input is guaranteed to be within the range from 1 to 3999.将罗马数字转为阿拉伯数字 对应转换表如下：个位数举例I, 1 】II, 2】 III, 3】 IV, 4 】V, 5 】VI, 6】 VII, 7】 VIII,8 】IX,

Given a list of non negative integers, arrange them such that they form the largest number.For example, given [3, 30, 34, 5, 9], the largest formed number is 9534330.Note: The result may be very

public class Solution { public List merge(List intervals) { if(intervals.size()<=1) return intervals; int i=0; while(i<intervals.size()){ Interval inti=intervals.get(i); int j=i+1

Given an integer n, generate a square matrix filled with elements from 1 to n2 in spiral order.For example,Given n = 3,You should return the following matrix:[ [ 1, 2, 3 ], [ 8, 9, 4 ], [

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

Given a matrix of m x n elements (m rows, n columns), return all elements of the matrix in spiral order.For example,Given the following matrix:[ [ 1, 2, 3 ], [ 4, 5, 6 ], [ 7, 8, 9 ]]

Given a m x n grid filled with non-negative numbers, find a path from top left to bottom right which minimizes the sum of all numbers along its path.Note: You can only move either down or right at

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

Given an array where elements are sorted in ascending order, convert it to a height balanced BST.将增序数组转换为左右均衡的二叉查找树 根据查找树的性质 左子树所有节点小于根节点值 右边都大于根节点值 子树也遵循此性质 所以只要取出增序数组的中间值作为根节点 再将左右子数组进行递归 代码如下：p

Implement regular expression matching with support for '.' and '*'.'.' Matches any single character.'*' Matches zero or more of the preceding element.The matching should cover the entire input

Given numRows, generate the first numRows of Pascal's triangle.For example, given numRows = 5,Return[ [1], [1,1], [1,2,1], [1,3,3,1], [1,4,6,4,1]]Pascal的每一层以1开始和结束 并且自第二位起 其值

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

Follow up for problem "Populating Next Right Pointers in Each Node".What if the given tree could be any binary tree? Would your previous solution still work?Note:You may only use constant

Given an index k, return the kth row of the Pascal's triangle.For example, given k = 3,Return [1,3,3,1].Note:Could you optimize your algorithm to use only O(k) extra space?与Pascal's Tr

Given two words (start and end), and a dictionary, find the length of shortest transformation sequence from start to end, such that:Only one letter can be changed at a timeEach intermediate word

Given an array S of n integers, find three integers in S such that the sum is closest to a given number, target. Return the sum of the three integers. You may assume that each input would have exact

Given an array S of n integers, are there elements a, b, c, and d in S such that a + b + c + d = target? Find all unique quadruplets in the array which gives the sum of target.Note:Element

Divide two integers without using multiplication, division and mod operator.If it is overflow, return MAX_INT.思路1：看样只能用减法了，依次减去除数，TOTS，肯定超时。思路2：每次减去N倍的除数，结果也加上N次，因此我们需要将除数扩大N倍。int扩展成long防止

Given a triangle, find the minimum path sum from top to bottom. Each step you may move to adjacent numbers on the row below.For example, given the following triangle[ [2], [3,4], [

Given a binary tree struct TreeLinkNode { TreeLinkNode *left; TreeLinkNode *right; TreeLinkNode *next; }Populate each next pointer to point to its next right node.

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

Given preorder and inorder traversal of a tree, construct the binary tree.Note:You may assume that duplicates do not exist in the tree.给出树的中序和先序遍历 要求返回树  中序结果｛1，2，5，4，3，6｝ 先序｛4，2，1，5，3，6｝根据先

Given inorder and postorder traversal of a tree, construct the binary tree.Note:You may assume that duplicates do not exist in the tree.还是重构树  与上一题相比  先序换成了后序  思路还是一样 代码如下：public class S

Given a singly linked list where elements are sorted in ascending order, convert it to a height balanced BST.将增序链表转换为均衡的二叉查找树 与数组转换相同 找到链表的中间结点 作为树的根节点进行赋值  再将链表以中间节点为界 分为左右子链表 进行递归赋值 代码如下：publi

Given a binary tree and a sum, find all root-to-leaf paths where each path's sum equals the given sum.For example:Given the below binary tree and sum = 22, 5 / \