coder 进阶的专栏

参考文章：http://blog.csdn.net/luckyxiaoqiang/article/details/7393134Leetcode 中 链表节点定义如下：struct ListNode {int val;ListNode *next;ListNode(int x) : val(x), next(NULL) {}};

题目：1. 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,

1.Gray CodeThe gray code is a binary numeral system where two successive values differ in only one bit.Given a non-negative integer n representing the total number of bits in the code, print

1. Sudoku Solverrite a program to solve a Sudoku puzzle by filling the empty cells.Empty cells are indicated by the character '.'.You may assume that there will be only one unique soluti

IdQuestionDifficultyFrequencyData StructuresAlgorithms1Two Sum25array + setsort + two pointers2Add Two Numbers34linked listtwo point

1. Recover Binary Search TreeTwo 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

1. Search for a RangeGiven a sorted array of integers, 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).

1. First Missing PositiveGiven an unsorted integer array, find the first missing positive integer.For example,Given [1,2,0] return 3,and [3,4,-1,1] return 2.Your algorithm should run

1. 常见数据结构线性：数组：Merge Sorted Array链表：Merge k Sorted Lists，Partition List队列，堆栈，块状数组（数组+链表），hash表，双端队列，位图（bitmap）树：　　　二叉树：　Minimum Depth of Binary Tree, Path Sum II, Inorder Trave

1.Palindrome NumberDetermine 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 yo

1. Generate ParenthesisGiven n pairs of parentheses, write a function to generate all combinations of well-formed parentheses.For example, given n = 3, a solution set is:"((()))", "(()()

1. Valid ParentheseGiven a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.The brackets must close in the correct order, "()"

参考文章：http://fisherlei.blogspot.com最近在刷LeetCode,开始刷题--面试--刷题。。。下面将遇到的可以用递归求解的问题归纳于此1. CombinationGiven two integers n and k, return all possible combinations of k numbers out of 1 ... n.

1. Valid SodokuDetermine 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 '.'.

1. Merge k sorted listsMerge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity.//Merge k sorted linked lists and return it as one sorted list. Analyze

1. 3SumGiven an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero.Note:Elements in a t

1. Clone GraphClone an undirected graph. Each node in the graph contains a label and a list of its neighbors.OJ's undirected graph serialization:Nodes are labeled uniquely.We use # a

1. Jump GameGiven 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 positi

1. Integer to RomanGiven an integer, convert it to a roman numeral.Input is guaranteed to be within the range from 1 to 3999.主要是按区间处理每一位digit1digit==4digit==55digit==9string in

1. Palindrome Partioning IIGiven a string s, partition s such that every substring of the partition is a palindrome.Return all possible palindrome partitioning of s.For example, given s 

Given n, generate all structurally unique BST's (binary search trees) that store values 1...n.For example,Given n = 3, your program should return all 5 unique BST's shown below. 1 3

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 / \

Given a singly linked list where elements are sorted in ascending order, convert it to a height balanced BST.

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

Given n, how many structurally unique BST's (binary search trees) that store values 1...n?For example,Given n = 3, there are a total of 5 unique BST's. 1 3 3 2 1 \

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

Length of last wordGiven 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, ret

Because the requirement "height balanced", this problem becomes relative easy.Just recursively use the middle element in the array as the root node of the current tree(sub tree).

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

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).For example,S = "ADOBECODEBANC"T = "ABC"Minimum window is "BAN

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 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 s1, s2, s3, find whether s3 is formed by the interleaving of s1 and s2.For example,Given:s1 = "aabcc",s2 = "dbbca",When s3 = "aadbbcbcac", return true.When s3 = "aadbbbaccc", ret

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.Th

Analysis:The idea is much similar to the previous question "Binary Tree Level Order Traversal", the only difference is the print order for each level. Note that we store the level order while traver

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.

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

Longest Consecutive SequenceGiven an unsorted array of integers, find the length of the longest consecutive elements sequence.For example,Given [100, 4, 200, 1, 3, 2],The longest consecu

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 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], [