经典算法题一览
0. 零基础入门
Coding interview exposed (3ed) 这个最简单了，基础比较挫的可以从这里开始
“这本书籍不是“课本”，不是“课程”，而是教你做各种常见面试题目的。熟练掌握这本书籍的内容，是你找到工作的基础。”
Programming Interviews Exposed 8.0/60 | 程序员面试攻略 7.7/86
MIT的Hacking a google interview（也非常简单）
1. 系统学习 - 不能满足于给出解法，复杂度分析一样重要
careercup不难，参考二爷划的重点，早早开始做，即使先开始做前几章简单的。
Cracking the Coding Interview v5 8.9/88
挑战程序设计竞赛 9.0/72
编程之美 8.3/2289
剑指offer 8.3/159
编程珠玑 9.2/1215
复杂度分析要善于总结归纳，不妨看看算法之排序算法，一图胜千言
2. 真题 - 时间有限，编码真题练手是最直接的。
最好的教材自然就是careercup （类似的网站还有glassdoor）
3. OJ - Bug Free&Code Style比攻克难题更重要
OJ有反馈保持手感，对非ACM选手，即使是google的面试也不会太难
leetcode的题稍难一些，不过很有趣，可以参考这份难度系数表刷题(文末有附)，还有一个tips(北美求职群主分类题解/九章的答案/maskray答案)
codility 有分类，可以锻炼举一反三能力，比Leetcode更适合入门
九度Online Judge （基于《剑指Offer》）
如果有余力，还有很多OJ网站：
interviewstreet （一些海外公司的笔试平台）
google code jam google面可以做做
4 简历和behavior question
What A GOOD Resume Should Look Like
The Google Resume 8.2/38 | 金领简历 8.2/20
behavior question，准备一些类似于自我介绍、为什么xx公司一类的就行，其它的知道怎么回答就行。http://hrinterviews.blogspot.com/ （64道behavior questions）。
5.系统设计
6.资讯
7. 网络资源
结构之法 算法之道 July的博客
程序员编程艺术 July的新书
剑指Offer：名企面试官精讲典型编程题 何海涛的博客
mitbbs的JobHunting版(需FQ)
大牛制定的MIT算法导论公开课学习计划，配套精选的ACM题
8.其他可供消(shao)遣(qian)的书籍
大话数据结构 8.1/336
大话设计模式 8.3/1139
鸟哥的Linux私房菜.基础学习篇 9.1/1097
UNIX环境高级编程 9.4/1531
UNIX编程艺术 9.1/1651
人人都有好工作 7.9/45
谁是谷歌想要的人才 7.4/195
浪潮之巅 9.1/10221
黑客与画家 8.8/7032
暗时间 8.5/4871
程序员面试宝典 6.1/118(强烈土豪购买这本用来烧钱...里面很多错误，找到就是赚到)
参考:
http://www.1point3acres.com/bbs/thread-50411-1-1.html
http://www.zzsec.org/tags.html#leetcode-ref
附：
leetcode Questions
| Id | Question | Difficulty | Freqency | Data Structures | Algorithms |
| 1 | Two Sum | 2 | 5 | array, set | sort, two pointers |
| 8 | String to Integer (atoi) | 2 | 5 | string | math |
| 20 | Valid Parentheses | 2 | 5 | string | stack |
| 21 | Merge Two Sorted Lists | 2 | 5 | linked list | sort, two pointers, merge |
| 65 | Valid Number | 2 | 5 | string | math |
| 70 | Climbing Stairs | 2 | 5 | dp | |
| 88 | Merge Sorted Array | 2 | 5 | array | two pointers, merge |
| 125 | Valid Palindrome | 2 | 5 | string | two pointers |
| 15 | 3Sum | 3 | 5 | array | two pointers |
| 50 | Pow(x, n) | 3 | 5 | binary search, math | |
| 73 | Set Matrix Zeroes | 3 | 5 | array | |
| 98 | Validate Binary Search Tree | 3 | 5 | tree | dfs |
| 127 | Word Ladder | 3 | 5 | graph | bfs, shortest path |
| 28 | Implement strStr() | 4 | 5 | string | two pointers, KMP, rolling hash |
| 56 | Merge Intervals | 4 | 5 | array, linked list, red-black tree | sort, merge |
| 57 | Insert Interval | 4 | 5 | array, linked list, red-black tree | sort, merge |
| 27 | Remove Element | 1 | 4 | array | two pointers |
| 13 | Roman to Integer | 2 | 4 | math | |
| 24 | Swap Nodes in Pairs | 2 | 4 | linked list | |
| 67 | Add Binary | 2 | 4 | string | two pointers, math |
| 129 | Sum Root to Leaf Numbers | 2 | 4 | tree | dfs |
| 2 | Add Two Numbers | 3 | 4 | linked list | two pointers, math |
| 12 | Integer to Roman | 3 | 4 | math | |
| 22 | Generate Parentheses | 3 | 4 | string | dfs |
| 23 | Merge k Sorted Lists | 3 | 4 | linked list, heap | sort, two pointers, merge |
| 46 | Permutations | 3 | 4 | array | permutation |
| 49 | Anagrams | 3 | 4 | string, hashtable | |
| 77 | Combinations | 3 | 4 | combination | |
| 78 | Subsets | 3 | 4 | array | recursion, combination |
| 79 | Word Search | 3 | 4 | array | dfs |
| 91 | Decode Ways | 3 | 4 | string | recursion, dp |
| 102 | Binary Tree Level Order Traversal | 3 | 4 | tree | bfs |
| 131 | Palindrome Partitioning | 3 | 4 | string | dfs |
| 69 | Sqrt(x) | 4 | 4 | binary search | |
| 26 | Remove Duplicates from Sorted Array | 1 | 3 | array | two pointers |
| 83 | Remove Duplicates from Sorted List | 1 | 3 | linked list | |
| 112 | Path Sum | 1 | 3 | tree | dfs |
| 7 | Reverse Integer | 2 | 3 | math | |
| 19 | Remove Nth Node From End of List | 2 | 3 | linked list | two pointers |
| 62 | Unique Paths | 2 | 3 | array | dp |
| 108 | Convert Sorted Array to Binary Search Tree | 2 | 3 | tree | dfs |
| 17 | Letter Combinations of a Phone Number | 3 | 3 | string | dfs |
| 39 | Combination Sum | 3 | 3 | array | combination |
| 53 | Maximum Subarray | 3 | 3 | array | dp |
| 63 | Unique Paths II | 3 | 3 | array | dp |
| 64 | Minimum Path Sum | 3 | 3 | array | dp |
| 74 | Search a 2D Matrix | 3 | 3 | array | binary search |
| 82 | Remove Duplicates from Sorted List II | 3 | 3 | linked list | recursion, two pointers |
| 86 | Partition List | 3 | 3 | linked list | two pointers |
| 93 | Restore IP Addresses | 3 | 3 | string | dfs |
| 105 | Construct Binary Tree from Preorder and Inorder Tr | 3 | 3 | array, tree | dfs |
| 106 | Construct Binary Tree from Inorder and Postorder T | 3 | 3 | array, tree | dfs |
| 114 | Flatten Binary Tree to Linked List | 3 | 3 | tree | recursion, stack |
| 116 | Populating Next Right Pointers in Each Node | 3 | 3 | tree | dfs |
| 29 | Divide Two Integers | 4 | 3 | binary search, math | |
| 33 | Search in Rotated Sorted Array | 4 | 3 | array | binary search |
| 34 | Search for a Range | 4 | 3 | array | binary search |
| 43 | Multiply Strings | 4 | 3 | string | two pointers |
| 51 | N-Queens | 4 | 3 | array | dfs |
| 52 | N-Queens II | 4 | 3 | array | dfs |
| 72 | Edit Distance | 4 | 3 | string | dp |
| 94 | Binary Tree Inorder Traversal | 4 | 3 | tree, hashtable | recursion, morris, stack |
| 103 | Binary Tree Zigzag Level Order Traversal | 4 | 3 | queue, tree | bfs, stack |
| 109 | Convert Sorted List to Binary Search Tree | 4 | 3 | linked list | recursion, two pointers |
| 128 | Longest Consecutive Sequence | 4 | 3 | array | |
| 130 | Surrounded Regions | 4 | 3 | array | bfs, dfs |
| 132 | Palindrome Partitioning II | 4 | 3 | string | dp |
| 4 | Median of Two Sorted Arrays | 5 | 3 | array | binary search |
| 10 | Regular Expression Matching | 5 | 3 | string | recursion, dp |
| 44 | Wildcard Matching | 5 | 3 | string | recursion, dp, greedy |
| 81 | Search in Rotated Sorted Array II | 5 | 3 | array | binary search |
| 66 | Plus One | 1 | 2 | array | math |
| 101 | Symmetric Tree | 1 | 2 | tree | dfs |
| 110 | Balanced Binary Tree | 1 | 2 | tree | dfs |
| 9 | Palindrome Number | 2 | 2 | math | |
| 35 | Search Insert Position | 2 | 2 | array | |
| 36 | Valid Sudoku | 2 | 2 | array | |
| 38 | Count and Say | 2 | 2 | string | two pointers |
| 80 | Remove Duplicates from Sorted Array II | 2 | 2 | array | two pointers |
| 113 | Path Sum II | 2 | 2 | tree | dfs |
| 3 | Longest Substring Without Repeating Characters | 3 | 2 | string, hashtable | two pointers |
| 11 | Container With Most Water | 3 | 2 | array | two pointers |
| 18 | 4Sum | 3 | 2 | array | |
| 55 | Jump Game | 3 | 2 | array | |
| 59 | Spiral Matrix II | 3 | 2 | array | |
| 61 | Rotate List | 3 | 2 | linked list | two pointers |
| 92 | Reverse Linked List II | 3 | 2 | linked list | two pointers |
| 5 | Longest Palindromic Substring | 4 | 2 | string | |
| 25 | Reverse Nodes in k-Group | 4 | 2 | linked list | recursion, two pointers |
| 37 | Sudoku Solver | 4 | 2 | array | dfs |
| 40 | Combination Sum II | 4 | 2 | array | combination |
| 42 | Trapping Rain Water | 4 | 2 | array | two pointers, stack |
| 45 | Jump Game II | 4 | 2 | array | |
| 47 | Permutations II | 4 | 2 | array | permutation |
| 48 | Rotate Image | 4 | 2 | array | |
| 54 | Spiral Matrix | 4 | 2 | array | |
| 68 | Text Justification | 4 | 2 | string | |
| 75 | Sort Colors | 4 | 2 | array | sort, two pointers |
| 76 | Minimum Window Substring | 4 | 2 | string | two pointers |
| 89 | Gray Code | 4 | 2 | combination | |
| 90 | Subsets II | 4 | 2 | array | recursion, combination |
| 99 | Recover Binary Search Tree | 4 | 2 | tree | dfs |
| 115 | Distinct Subsequences | 4 | 2 | string | dp |
| 117 | Populating Next Right Pointers in Each Node II | 4 | 2 | tree | dfs |
| 124 | Binary Tree Maximum Path Sum | 4 | 2 | tree | dfs |
| 31 | Next Permutation | 5 | 2 | array | permutation |
| 41 | First Missing Positive | 5 | 2 | array | sort |
| 84 | Largest Rectangle in Histogram | 5 | 2 | array | stack |
| 87 | Scramble String | 5 | 2 | string | recursion, dp |
| 97 | Interleaving String | 5 | 2 | string | recursion, dp |
| 58 | Length of Last Word | 1 | 1 | string | |
| 100 | Same Tree | 1 | 1 | tree | dfs |
| 104 | Maximum Depth of Binary Tree | 1 | 1 | tree | dfs |
| 111 | Minimum Depth of Binary Tree | 1 | 1 | tree | dfs |
| 126 | Word Ladder II | 1 | 1 | ||
| 14 | Longest Common Prefix | 2 | 1 | string | |
| 118 | Pascal's Triangle | 2 | 1 | array | |
| 119 | Pascal's Triangle II | 2 | 1 | array | |
| 121 | Best Time to Buy and Sell Stock | 2 | 1 | array | dp |
| 6 | ZigZag Conversion | 3 | 1 | string | |
| 16 | 3Sum Closest | 3 | 1 | array | two pointers |
| 30 | Substring with Concatenation of All Words | 3 | 1 | string | two pointers |
| 71 | Simplify Path | 3 | 1 | string | stack |
| 96 | Unique Binary Search Trees | 3 | 1 | tree | dp |
| 107 | Binary Tree Level Order Traversal II | 3 | 1 | tree | bfs |
| 120 | Triangle | 3 | 1 | array | dp |
| 122 | Best Time to Buy and Sell Stock II | 3 | 1 | array | greedy |
| 32 | Longest Valid Parentheses | 4 | 1 | string | dp |
| 95 | Unique Binary Search Trees II | 4 | 1 | tree | dp, dfs |
| 123 | Best Time to Buy and Sell Stock III | 4 | 1 | array | dp |
| 60 | Permutation Sequence | 5 | 1 | permutation, math | |
| 85 | Maximal Rectangle | 5 | 1 | array | dp, stack |
很可惜二爷不再更新了，未名上Jc2013补充了一点新题
1. Clone Graph-> BFS+HashMap
2. Gas Station->DP
3. Candy->Two Pointers
4. Single Number-> Xor, HashMap, or Sum or Product way to find
5. Single Number II -> Xor, HashMap
6. Copy List with Random Pointers -> Two Pointers, HashMap with two times
traverse(like clone graph)
7. List Cycle, List Cycle II, Reorder List-> Two Pointers
8. Binary Tree Preorder, Postorder recursive -> Using stack to mock
recursive way, or implement like morris way.
9. LRU Cache-> HashMap + list
10. Insertion sort list -> Two Pointers
11. Sort List-> I implement merge sort, still, two pointers method,
combination of merge sort list and split
list
12. Word Break -> DFS DP
13. Word Break II -> DP + Backtracking
很多人都说把这150题做了一遍或几遍，但是我感觉算法题才是重点，其他的很多题面
试基本碰不上，没看出来有必要全做。这里总结一下自己认为重要的题。
第一章 ：
全部重要 (1.6, 1.7 Leetcode上有）。
1.5 面A碰到 (string compression)
1.7面Z碰到 (set 0)
1.8面Bigfish碰到 (string rotation)
第二章 (2.4, 2.5 Leetcode上有）：
全部重要。
2.2面Bigfish碰到 (find kth)
第三章 ：
感觉就是3.2 (min stack), 3.5 (two stack queue) 重要。两道题面M被问到过。3.6
(sort stack)感觉也有可能被考到。
第四章 （4.1， 4.3， 4.5 Leetcode上有）：
感觉4.2, 4.3, 4.5，4.6， 4.7 重要。4.5 (valid BST)面E，Q碰到过
第五章：5.4 (n & (n-1))
第六章：6.5 (drop egg)
第七章：7.3 (line intersection)，7.6 (line passes most points)
第八章：8.4 (parking lot)， 8.10 (hashtable)
第九章 （9.1， 9.2， 9.5， 9.6，9.8，9.9 Leetcode上有）：
感觉都重要 （9.10 (stack of boxes)， 9.11 (boolean expression) 貌似可以忽略
）。
第十章（10.1， 10.2， 10.3 Leetcode上有）：
10.1 (merge) M碰到过两次
10.3
10.4 (external sort) E碰到
10.6
第十七章（17.8， 17.12, 17.13 Leetcode上有）：
17.1 (swap number)
17.2 (tic-tac-toe) 面I遇到过
17.7 (integer->english)
17.8 (largest sum) 经典， 注意变形题 (largest product), 面RF碰到过
17.9 (frequency of occurrences) S碰到
17.11 (rand7)
17.12 (2 sum) G碰到
17.13 (BT -> Linkedlist)
第十八章（9）：
18.2 (shuffle deck) 貌似经典
18.3 (random)
18.4 (count 2s) 注意思路，可能会出现类似题
18.5 (shortest distance)
18.6 (quick select) 面Z, G碰到类似题
18.9－18.12
一共50道题。其他很多题可以做练习，但是面试碰到的概率不大。上边一些题面试也很
难碰到但是是不可不练的题，比如八皇后。另外就是别完全follow书上的答案，注意看
有没有bug。希望大家能补充一下自己认为重要的。
二爷的DP总结
“不断看到有新人学习DP，想谈谈我的感受。
我大概是去年底，今年初开始学习DP的。以前没有一点概念。去年G电面我的时候就出
了一道最简单的DP题，那时我根本不知道什么是DP，在提示下用recursion做出来的，
没有用cache。
开始学习DP是在careercup 150那本书上。下面是一些感受。
1. careercup定义的DP就是recursion+cache。这个定义指导了我很长时间。我认为这
个定义是DP的初级阶段，有误导性，使得我在练习的时候发现很多题型用这个定义套不
上。误导性在于： 1, recursion+cache是DP不错，但是DP并不等于recursion+cache。
2, recursion的DP并不优化，因此从recursion出发做DP不是个好思路。
2. 我后来理解的DP是这样子的。很简单就是推DP公式。也就是说怎么用F(n-i) 推导出
F(n)来。当然这也是最难的。发现很多难题还是很难想到这个公式的，可能就得多练习
了，培养思路。这个定义跟careercup上的不一样的地方主要是思考的方式不同，一个
是推公式，一个是找recursion的办法。而DP的关键是推公式，如果从recursion出发的
话，很多题可能做不出来。
做DP题需要注意两点：
1. 能用iteration就不要用recursion。这也证明了careercup上的定义有局限性了。
2. DP是用空间换时间。所以DP题做熟了，应该考虑怎样优化空间了。能用常数空间就
不要用O(n), 能用O(n)就不要用O(n^2). (我觉得这也是Vissa的霸气所在。Vissa面F
的时候说过“这么简单的DP题，我从来都是用常数空间”）。
最后就是多做题才能培养思路。一般面试应该不会有很难的DP题，多练习一下有了思路
，再能写出iteration和空间优化的解法，并且能保证少bug的话，应该面试就差不多了。”
