春招~~~Leetcode按类型刷题（内附刷题顺序表）

Leetcode 分类顺序Array[td]

基础
27	Remove Element
26	Remove Duplicates from Sorted Array
80	Remove Duplicates from Sorted Array II
277	Find the Celebrity
189	Rotate Array
41	First Missing Positive
299	Bulls and Cows
134	Gas Station
118	Pascal's Triangle	很少考
119	Pascal's Triangle II	很少考
169	Majority Element	很少考
229	Majority Element II	很少考
274	H-Index
275	H-Index II	Binary Search
243	Shortest Word Distance
244	Shortest Word Distance II
245	Shortest Word Distance III
217	Contains Duplicate
219	Contains Duplicate II	很少考
220	Contains Duplicate III	很少考
55	Jump Game
45	Jump Game II
121	Best Time to Buy and Sell Stock
122	Best Time to Buy and Sell Stock II
123	Best Time to Buy and Sell Stock III
188	Best Time to Buy and Sell Stock IV
309	Best Time to Buy and Sell Stock with Cooldown
11	Container With Most Water
42	Trapping Rain Water
334	Increasing Triplet Subsequence
128	Longest Consecutive Sequence
164	Maximum Gap	Bucket
287	Find the Duplicate Number
135	Candy	很少考
330	Patching Array	很少考
提高
4	Median of Two Sorted Arrays
321	Create Maximum Number	很少考
327	Count of Range Sum	很少考
289	Game of Life
Interval
57	Insert Interval
56	Merge Intervals
252	Meeting Rooms
253	Meeting Rooms II
352	Data Stream as Disjoint Intervals	TreeMap
Counter
239	Sliding Window Maximum
295	Find Median from Data Stream
53	Maximum Subarray
325	Maximum Size Subarray Sum Equals k
209	Minimum Size Subarray Sum
238	Product of Array Except Self
152	Maximum Product Subarray
228	Summary Ranges
163	Missing Ranges
Sort
88	Merge Sorted Array
75	Sort Colors
283	Move Zeroes
376	Wiggle Subsequence
280	Wiggle Sort
324	Wiggle Sort II

String[td]

基础
28	Implement strStr()
14	Longest Common Prefix
58	Length of Last Word
387	First Unique Character in a String
383	Ransom Note
344	Reverse String
151	Reverse Words in a String
186	Reverse Words in a String II
345	Reverse Vowels of a String
205	Isomorphic Strings
293	Flip Game
294	Flip Game II
290	Word Pattern
242	Valid Anagram
49	Group Anagrams
249	Group Shifted Strings
87	Scramble String
179	Largest Number	很少考
6	ZigZag Conversion	很少考
161	One Edit Distance
38	Count and Say
358	Rearrange String k Distance Apart
316	Remove Duplicate Letters
271	Encode and Decode Strings
168	Excel Sheet Column Title
171	Excel Sheet Column Number
13	Roman to Integer
12	Integer to Roman
273	Integer to English Words
246	Strobogrammatic Number
247	Strobogrammatic Number II
248	Strobogrammatic Number III	很少考
提高
68	Text Justification
65	Valid Number
157	Read N Characters Given Read4
158	Read N Characters Given Read4 II - Call multiple times
Substring
76	Minimum Window Substring	Sliding Window
30	Substring with Concatenation of All Words	Sliding Window
3	Longest Substring Without Repeating Characters	Sliding Window
340	Longest Substring with At Most K Distinct Characters	Sliding Window
395	Longest Substring with At Least K Repeating Characters	Sliding Window
159	Longest Substring with At Most Two Distinct Characters	Sliding Window
Palindrome
125	Valid Palindrome
266	Palindrome Permutation
5	Longest Palindromic Substring
9	Palindrome Number
214	Shortest Palindrome
336	Palindrome Pairs
131	Palindrome Partitioning
132	Palindrome Partitioning II
267	Palindrome Permutation II
Parentheses
20	Valid Parentheses
22	Generate Parentheses
32	Longest Valid Parentheses
241	Different Ways to Add Parentheses
301	Remove Invalid Parentheses
Subsequence
392	Is Subsequence
115	Distinct Subsequences
187	Repeated DNA Sequences	很少考

Math[td]

基础
7	Reverse Integer
165	Compare Version Numbers
66	Plus One
8	String to Integer (atoi)
258	Add Digits
67	Add Binary
43	Multiply Strings
29	Divide Two Integers
69	Sqrt(x)
50	Pow(x, n)
367	Valid Perfect Square
365	Water and Jug Problem
204	Count Primes
Sum
1	Two Sum
167	Two Sum II - Input array is sorted
15	3Sum
16	3Sum Closest	很少考
259	3Sum Smaller	很少考
18	4Sum
很少考
231	Power of Two
326	Power of Three
342	Power of Four
372	Super Pow
233	Number of Digit One
319	Bulb Switcher
292	Nim Game
202	Happy Number
400	Nth Digit
263	Ugly Number
264	Ugly Number II
306	Additive Number
172	Factorial Trailing Zeroes
343	Integer Break
396	Rotate Function
390	Elimination Game
386	Lexicographical Numbers
357	Count Numbers with Unique Digits
360	Sort Transformed Array
397	Integer Replacement
368	Largest Divisible Subset

Tree[td]

基础
144	Binary Tree Preorder Traversal	preorder
94	Binary Tree Inorder Traversal	Inorder
145	Binary Tree Postorder Traversal	postorder
102	Binary Tree Level Order Traversal	DFS + BFS
Preorder
100	Same Tree	preorder
101	Symmetric Tree	preorder
226	Invert Binary Tree	preorder + BFS
257	Binary Tree Paths	preorder
112	Path Sum	preorder
113	Path Sum II	preorder
129	Sum Root to Leaf Numbers	preorder
298	Binary Tree Longest Consecutive Sequence	preorder
111	Minimum Depth of Binary Tree	preorder
Postorder
104	Maximum Depth of Binary Tree	postorder
110	Balanced Binary Tree	postorder
124	Binary Tree Maximum Path Sum	postorder
250	Count Univalue Subtrees	postorder
366	Find Leaves of Binary Tree	postorder
337	House Robber III	postorder + preorder
BFS
107	Binary Tree Level Order Traversal II	BFS
103	Binary Tree Zigzag Level Order Traversal	BFS
199	Binary Tree Right Side View	BFS + preorder
BST
98	Validate Binary Search Tree	preorder
235	Lowest Common Ancestor of a Binary Search Tree	preorder
236	Lowest Common Ancestor of a Binary Tree	postorder
108	Convert Sorted Array to Binary Search Tree	binary search
109	Convert Sorted List to Binary Search Tree	binary search
173	Binary Search Tree Iterator	inorder
230	Kth Smallest Element in a BST	inorder
297	Serialize and Deserialize Binary Tree	BFS
285	Inorder Successor in BST	inorder
270	Closest Binary Search Tree Value	preorder
272	Closest Binary Search Tree Value II	inorder
99	Recover Binary Search Tree	inorder
重要程度
156	Binary Tree Upside Down	很少考
114	Flatten Binary Tree to Linked List	很少考
255	Verify Preorder Sequence in Binary Search Tree	很少考
333	Largest BST Subtree	很少考
222	Count Complete Tree Nodes	很少考
105	Construct Binary Tree from Preorder and Inorder Traversal	很少考
106	Construct Binary Tree from Inorder and Postorder Traversal	很少考
116	Populating Next Right Pointers in Each Node	重要
117	Populating Next Right Pointers in Each Node II	重要
314	Binary Tree Vertical Order Traversal	重要
96	Unique Binary Search Trees	重要
95	Unique Binary Search Trees II	很少考
331	Verify Preorder Serialization of a Binary Tree	很少考

Backtracking[td]

基础
78	Subsets
90	Subsets II
77	Combinations
39	Combination Sum
40	Combination Sum II
216	Combination Sum III
377	Combination Sum IV	Dynamic Programming
254	Factor Combinations
46	Permutations
47	Permutations II
31	Next Permutation	String
60	Permutation Sequence	String
291	Word Pattern II
Enumeration
17	Letter Combinations of a Phone Number
320	Generalized Abbreviation	要重录
93	Restore IP Addresses	很少考
282	Expression Add Operators
140	Word Break II
351	Android Unlock Patterns

Dynamic Programming[td]

一维
70	Climbing Stairs
62	Unique Paths
63	Unique Paths II
120	Triangle	很少考
279	Perfect Squares
139	Word Break
375	Guess Number Higher or Lower II
312	Burst Balloons
322	Coin Change
二维
256	Paint House
265	Paint House II
64	Minimum Path Sum
72	Edit Distance
97	Interleaving String
174	Dungeon Game
221	Maximal Square
85	Maximal Rectangle
363	Max Sum of Rectangle No Larger Than K	TreeSet
化简
198	House Robber
213	House Robber II
276	Paint Fence
91	Decode Ways
10	Regular Expression Matching
44	Wildcard Matching

LinkedList[td]

基础
206	Reverse Linked List
141	Linked List Cycle
24	Swap Nodes in Pairs
328	Odd Even Linked List
92	Reverse Linked List II
237	Delete Node in a Linked List
19	Remove Nth Node From End of List
83	Remove Duplicates from Sorted List
203	Remove Linked List Elements
82	Remove Duplicates from Sorted List II
369	Plus One Linked List
2	Add Two Numbers
160	Intersection of Two Linked Lists
21	Merge Two Sorted Lists
提高
234	Palindrome Linked List
143	Reorder List
142	Linked List Cycle II
148	Sort List
25	Reverse Nodes in k-Group
61	Rotate List
86	Partition List
23	Merge k Sorted Lists
147	Insertion Sort List

Binary Search[td]

基础
278	First Bad Version
35	Search Insert Position
33	Search in Rotated Sorted Array
81	Search in Rotated Sorted Array II
153	Find Minimum in Rotated Sorted Array
154	Find Minimum in Rotated Sorted Array II
162	Find Peak Element
374	Guess Number Higher or Lower
34	Search for a Range
349	Intersection of Two Arrays
350	Intersection of Two Arrays II
315	Count of Smaller Numbers After Self
300	Longest Increasing Subsequence
354	Russian Doll Envelopes

Matrix[td]

48	Rotate Image
54	Spiral Matrix
59	Spiral Matrix II
73	Set Matrix Zeroes
311	Sparse Matrix Multiplication
329	Longest Increasing Path in a Matrix
378	Kth Smallest Element in a Sorted Matrix
74	Search a 2D Matrix
240	Search a 2D Matrix II
370	Range Addition
79	Word Search
296	Best Meeting Point
361	Bomb Enemy
317	Shortest Distance from All Buildings
302	Smallest Rectangle Enclosing Black Pixels
36	Valid Sudoku
37	Sudoku Solver

DFS & BFS[td]

基础
200	Number of Islands
286	Walls and Gates
130	Surrounded Regions
339	Nested List Weight Sum
364	Nested List Weight Sum II
127	Word Ladder
51	N-Queens
52	N-Queens II
126	Word Ladder II

Stack & PriorityQueue[td]

Stack
155	Min Stack
232	Implement Queue using Stacks
225	Implement Stack using Queues
150	Evaluate Reverse Polish Notation
71	Simplify Path
388	Longest Absolute File Path
394	Decode String
224	Basic Calculator
227	Basic Calculator II
385	Mini Parser
84	Largest Rectangle in Histogram
PriorityQueue
215	Kth Largest Element in an Array
347	Top K Frequent Elements
313	Super Ugly Number	很少考
373	Find K Pairs with Smallest Sums	很少考
218	The Skyline Problem
332	Reconstruct Itinerary
341	Flatten Nested List Iterator

Bit Manipulation[td]

基础
389	Find the Difference
136	Single Number
318	Maximum Product of Word Lengths
很少考
393	UTF-8 Validation
201	Bitwise AND of Numbers Range
371	Sum of Two Integers
338	Counting Bits
89	Gray Code
268	Missing Number
191	Number of 1 Bits
190	Reverse Bits
137	Single Number II
260	Single Number III

Topological Sort[td]

基础
207	Course Schedule
210	Course Schedule II
269	Alien Dictionary

Random[td]

基础
模板	Reservoir Sampling
384	Shuffle an Array
398	Random Pick Index
382	Linked List Random Node
380	Insert Delete GetRandom O(1)
381	Insert Delete GetRandom O(1) - Duplicates allowed
138	Copy List with Random Pointer

Graph[td]

基础
133	Clone Graph
399	Evaluate Division
310	Minimum Height Trees
图形学
335	Self Crossing	很少考
149	Max Points on a Line
356	Line Reflection	很少考
391	Perfect Rectangle	很少考
223	Rectangle Area	很少考

Union FInd[td]

基础
261	Graph Valid Tree
323	Number of Connected Components in an Undirected Graph
305	Number of Islands II

Trie[td]

基础
211	Add and Search Word - Data structure design
208	Implement Trie (Prefix Tree)
212	Word Search II

Design[td]

基础
359	Logger Rate Limiter
346	Moving Average from Data Stream	Sliding Window
362	Design Hit Counter
281	Zigzag Iterator
284	Peeking Iterator
251	Flatten 2D Vector
288	Unique Word Abbreviation
170	Two Sum III - Data structure design
348	Design Tic-Tac-Toe
379	Design Phone Directory
353	Design Snake Game
146	LRU Cache
355	Design Twitter
303	Range Sum Query - Immutable
304	Range Sum Query 2D - Immutable
307	Range Sum Query - Mutable	Binary Index Tree
308	Range Sum Query 2D - Mutable	Binary Index Tree

27. Remove Element
这道题输入时一个int array和一个int val；我们需要在这个array中in place删除给定的这个val; 然后返回一个长度，在这个长度内的所有元素必须不能包含需要删除的val；因为这道题不需要保留长度内order和原int order一致，所以有两种方法。
Int I = 0;
Int n = nums.length;
一种想法是用while(i<n)循环，一旦发现当前所在位置是需要remove的元素，就把这个位置的元素换成n所在的元素，然后n--；如果当前所在位置不是要remove的元素，就i++; 这样最终n就是最终返回的长度。这种做法在长度内是无法保持order的，因为我们总是从array最后取元素进来。
class Solution {
    public int removeElement(int[] nums, int val) {
        if(nums == null || nums.length == 0)
            return 0;
        
        int i = 0;
        int n = nums.length;
        while(i<n){
            if(nums[i] == val){
                nums[i] = nums[n-1];
                n--;
            }else{
                i++;
            }
        }
        return n;
    }
}
另外一种想法就是用一个变量（假设我们叫他res吧）去记录我们下一次需要挪到元素时的位置。我们用一个for loop循环一遍整个array，如果出现nums[i] != val的话，我们就把nums[res++] = nums[i]. 这背后的思想是如果我们nums[i]是需要移除的元素val的话，我们是不需要移动res的，因为这就是我们下一次需要挪动元素的位置。
class Solution {
    public int removeElement(int[] nums, int val) {
        if(nums == null || nums.length == 0)
            return 0;
        
        int res = 0;
        for(int i=0;i<nums.length;i++){
            if(nums[i] != val){
                nums[res++] = nums[i];
            }
        }
        return res;
    }
}

但是对于这种题目本身而言的话，我个人倾向于选择第二种思考方式，因为这种方式既能保持长度内顺序不变，再者呢，这是个消除元素算法的general thinking.

26. Remove Duplicates from Sorted Array
这道题和Leetcode 80题的思想是一样的，代码也只需要修改几行。
首先我们的input是一个int数组，而且是一个sorted array，这也就意味着我们的duplicates一定是在相邻的index。我们还是按照Leetcode 27题第二种放大的打致思想来做，首先我们需要一个变量来记录我们需要replace的位置。duplicates是有至少两个以上的同样val的element；消除duplicate不是消除element，所以我们要把duplicate里的第二个位置当做replace的index。这也就是说我们需要一个变量（假设我们加它res）初始值为1.也就是这个array里面第二个值。这是我们最先replace的index。然后我们从i=1开始循环一遍数组，一旦发现nums[i]的值和nums[res-1]的值不相等，我们就把res[i++] = nums[i]; 让我们反过来想，如果nums[i] == nums[res-1]意味着什么，意味着我们现在我们有两个duplicates，我们不能改变res的位置。然后i++，下一次找到nums[i] ！= nums[res-1]时候，我们就把duplicate消除了，然后我们res++。这样每次比较res-1的位置和i的值就能不断保证整个res之前的数组都是没有duplicates的。
class Solution {
    public int removeDuplicates(int[] nums) {
        if(nums == null || nums.length <= 1)
            return nums.length;
        
        int res = 1;
        for(int i=0;i<nums.length;i++){
            if(nums[i] != nums[res-1])
                nums[res++] = nums[i];
        }
        return res;
    }
}

80. Remove Duplicates from Sorted Array II
这道题和Leetcode 26题目一模一样，只加了一个要求就是，duplicates定义变成至少三个才叫duplicates。
那么，我们还是之前的思路，用一个变量记录需要replace的位置（叫他res），初始值就是array里第三个位置，也就是2.
从i=2循环一遍数组，如果有nums[i] != nums[res-2], 就nums[res++] = nums[i];
还是反过来想，如果nums[i] == nums[res-2],意味着什么我们有两个元素相等了，但还需要一个元素来使成为duplicates。这个时候我们要i++然后看nums[i] == nums[res-2]。因为i变大了一个，这个时候，她们如果还相等说明，我们找到duplicates啦，所以我们不改变res的值。等到下一次nums[i] ！= nums[res-2]，我们就进行replace的动作。
class Solution {
    public int removeDuplicates(int[] nums) {
        if(nums == null || nums.length <= 2)
            return nums.length;
        
        int res = 2;
        for(int i=2;i<nums.length;i++){
            if(nums[i] != nums[res-2]){
                nums[res++] = nums[i];
            }
        }
        return res;
    }
}

这个不错！刚开始刷题，楼主觉得刷题应该按类型刷，还是按top排行刷呢？？

Jennyy 发表于 2019-2-3 15:37
这个不错！刚开始刷题，楼主觉得刷题应该按类型刷，还是按top排行刷呢？？

分类top不就行了么

这个考的频率是指的所有公司还是特指某一个公司的面试？