leetcode练习题

所有题目列表

solution # 题目 难度 解答 备注
1 Two Sum 100
2 Add Two Numbers 80
3 Longest Substring Without Repeating Characters - 这个系列的所有题都要多做几遍
4 Median of Two Sorted Arrays 70 这题很经典，多做几遍
5 Longest Palindromic Substring 85 这题对比动态规划和最优算法
6 ZigZag Conversion
7 Reverse Integer 95
8 String to Integer (atoi) 90 很考代码能力，容易错
9 Palindrome Number
通过 10 正则表达式匹配 60 递归法 这题很经典，多做几遍，和#44一起
11 Container With Most Water
12 Integer to Roman
13 Roman to Integer
14 Longest Common Prefix 双指针
通过 15 3Sum 70
16 3Sum Closest
通过 17 Letter Combinations of a Phone Number 85 递归/回溯：最后一次递归才加入结果列表
18 4Sum
两次遍历法待做 19 删除链表的倒数第N个节点 medium 两次遍历法/一次遍历算法 两次遍历法和一次遍历法
20 有效的括号 100
21 Merge Two Sorted Lists 90
22 Generate Parentheses 80 这题看两遍
23 Merge k Sorted Lists 70
24 Swap Nodes in Pairs
25 Reverse Nodes in k-Group 80
26 Remove Duplicates from Sorted Array 80
27 Remove Element
28 Implement strStr() 70
29 Divide Two Integers
30 Substring with Concatenation of All Words
31 Next Permutation
32 Longest Valid Parentheses
33 Search in Rotated Sorted Array 80
34 Search for a Range
35 Search Insert Position
36 Valid Sudoku 80
37 Sudoku Solver 70 这道题是典型的back tracking，多做几遍
38 Count and Say 80
39 Combination Sum 70 排列组合系列的题要多做几遍
40 Combination Sum II 70
41 First Missing Positive
42 Trapping Rain Water 95
43 Multiply Strings 80
44 Wildcard Matching 60 和#10多做几遍
45 Jump Game II
46 Permutations
47 Permutations II 70 多做几遍
48 Rotate Image 100
49 Group Anagrams 95
50 Pow(x, n) 80
51 N-Queens
52 N-Queens II
通过 53 最大子序和 easy 动态规划法 DP算法 : T=O(N),S=O(1).利用nums数组本身作为DP数组
54 Spiral Matrix 85
55 Jump Game 贪心法
56 Merge Intervals 70
57 Insert Interval 75 这题要多做几遍
60 Permutation Sequence 70 这题思路巧妙，多做两遍
61 Rotate List 90
通过 62 不同的路径 medium 排列组合法/DP算法 排列组合法: 将机器人行列要走的轨迹当作要选择的方块
通过 63 不同的路径2 medium DP算法 DP算法,可以利用原先矩阵将空间复杂度降为 O(1)
66 Plus One 100 这题多看一遍
67 Add Binary 100
68 Text Justification
69 Sqrt(x) 85
通过 70 爬楼梯 easy 迭代法/动态规划法/递归法
71 Simplify Path 80
72 Edit Distance 75
73 Set Matrix Zeroes 90
74 Search a 2D Matrix
75 Sort Colors 65 这题多做几遍，很有意思
76 Minimum Window Substring 50 这题以及类似的题一定要多做几遍，很经典，参见window
77 Combinations
78 Subsets 85
79 Word Search 85
80 Remove Duplicates from Sorted Array II 100
81 Search in Rotated Sorted Array II 70
82 Remove Duplicates from Sorted List II 75
83 Remove Duplicates from Sorted List 100
84 Largest Rectangle in Histogram 70
85 Maximal Rectangle 75
86 Partition List 90
88 Merge Sorted Array 100
90 Subsets II 80
91 Decode Ways 75 这题多做几遍，包括#639
92 Reverse Linked List II 80
93 Restore IP Addresses 80 多看两遍
94 Binary Tree Inorder Traversal 100
95 Unique Binary Search Trees II 70 多做几遍，递归和DP
96 Unique Binary Search Trees 80
98 Validate Binary Search Tree 85 注意溢出
99 Recover Binary Search Tree 60 这题很容易错，要多做几遍
100 Same Tree 100
101 对称二叉树 95
102 Binary Tree Level Order Traversal 85
103 Binary Tree Zigzag Level Order Traversal 80
104 二叉树的最大深度 100
105 Construct Binary Tree from Preorder and Inorder Traversal 95
106 Construct Binary Tree from Inorder and Postorder Traversal 90
107 Binary Tree Level Order Traversal II 100
108 Convert Sorted Array to Binary Search Tree 100
109 Convert Sorted List to Binary Search Tree 90
110 平衡二叉树 80
111 Minimum Depth of Binary Tree 80
112 Path Sum 85
113 Path Sum II 65 错了好几次，得多做几遍
114 Flatten Binary Tree to Linked List 80
116 Populating Next Right Pointers in Each Node 80
117 Populating Next Right Pointers in Each Node II 80
118 Pascal's Triangle 80
119 Pascal's Triangle II 80
通过 120 三角形最小路径和 medium 基本的dp算法 自上而下，自下而上的方法，可用 dp[][],dp[] 两种辅助空间
121 Best Time to Buy and Sell Stock 100
122 Best Time to Buy and Sell Stock II 100
123 Best Time to Buy and Sell Stock III 75
124 Binary Tree Maximum Path Sum 60
125 Valid Palindrome 100
126 Word Ladder II
127 Word Ladder 70 此题非常经典，务必连同ii多做几遍，将双端BFS吃透
128 Longest Consecutive Sequence 60
129 Sum Root to Leaf Numbers 100
130 Surrounded Regions 65
131 Palindrome Partitioning
132 Palindrome Partitioning II
133 Clone Graph 70 这题不难，多看两遍，BFS方法再做两遍
135 Candy 80
138 Copy List with Random Pointer 95 有一个易错点
139 Word Break 80 多看两遍
140 Word Break II 75 这题多做两遍，很典型
141 Linked List Cycle 75
142 Linked List Cycle II 90
143 Reorder List 90
144 Binary Tree Preorder Traversal 85
145 Binary Tree Postorder Traversal 80
146 LRU Cache 95 好题目，多做几遍
147 Insertion Sort List 90
148 Sort List 90
149 Max Points on a Line 60
150 Evaluate Reverse Polish Notation 70
151 Reverse Words in a String 70 这题虽然不难，但是也错了几次
152 Maximum Product Subarray
153 Find Minimum in Rotated Sorted Array
154 Find Minimum in Rotated Sorted Array II
155 Min Stack 95
156 Binary Tree Upside Down 70 这道题挺有意思，多做几遍
157 Read N Characters Given Read4 80 这题多做几遍，结合#158
158 Read N Characters Given Read4 II - Call multiple times 70
159 Longest Substring with At Most Two Distinct Characters 100 多看两遍
160 Intersection of Two Linked Lists 100
161 One Edit Distance 85 和#72做两遍
162 Find Peak Element 90
163 Missing Ranges 65 多做几遍，太容易错了
164 Maximum Gap 65
167 Two Sum II - Input array is sorted 100
168 Excel Sheet Column Title
169 Majority Element 100
170 Two Sum III - Data structure design 100 这道题再多做一遍
171 Excel Sheet Column Number
172 Factorial Trailing Zeroes 100
173 Binary Search Tree Iterator 70 多留意一下
179 Largest Number 90
186 Reverse Words in a String II 90
188 Best Time to Buy and Sell Stock IV
189 Rotate Array 100
190 Reverse Bits 85
198 打家劫舍 80
199 Binary Tree Right Side View 80
200 Number of Islands 85 这道题很经典，而且方法不止一种，每种方法都多做几遍，包括UF，#305
203 Remove Linked List Elements
204 Count Primes 85
206 Reverse Linked List 90
207 Course Schedule 100 典型的拓扑排序
208 Implement Trie (Prefix Tree) 80 和#211多留意，trie很典型
209 Minimum Size Subarray Sum 85
210 Course Schedule II 95
211 Add and Search Word - Data structure design 85
212 Word Search II
213 House Robber II 80
214 Shortest Palindrome
215 Kth Largest Element in an Array 65 这题很经典，三种解法都要了然于胸
216 Combination Sum III 65
217 Contains Duplicate 100
218 The Skyline Problem 60 这题多做两遍
219 Contains Duplicate II 95
220 Contains Duplicate III 65
221 Maximal Square 80
222 Count Complete Tree Nodes 70 一般的做法会超时
223 Rectangle Area 95
224 Basic Calculator 80
225 Implement Stack using Queues 90
226 Invert Binary Tree 80
228 Summary Ranges 70
229 Majority Element II 70
230 Kth Smallest Element in a BST 85 注意Follow Up
232 Implement Queue using Stacks 95
233 Number of Digit One
234 Palindrome Linked List 75
235 Lowest Common Ancestor of a Binary Search Tree 100
236 Lowest Common Ancestor of a Binary Tree 50 这题很经典，多做几遍，留意节点不在树中的情况
237 Delete Node in a Linked List 100
238 Product of Array Except Self 85
239 Sliding Window Maximum 75 这题非常经典，多做几遍，包括常规算法(优先队列，treemap)及优化算法双端队列
240 Search a 2D Matrix II 100
241 Different Ways to Add Parentheses
242 Valid Anagram 100
243 Shortest Word Distance 80
244 Shortest Word Distance II 80
245 Shortest Word Distance III 80
246 Strobogrammatic Number 70 #247一个系列，多看两遍
247 Strobogrammatic Number II 70 多看两遍
249 Group Shifted Strings
250 Count Univalue Subtrees 70 这题要多做几遍
251 Flatten 2D Vector 100
252 Meeting Rooms 100
253 Meeting Rooms II 90
254 Factor Combinations 80
255 Verify Preorder Sequence in Binary Search Tree 85 很简单，粗心错了
256 Paint House 95
257 Binary Tree Paths 80
259 3Sum Smaller 95 这题虽然简单，但是因为思维定式还是错了几次
261 Graph Valid Tree 70 这题多做几遍
263 Ugly Number 85
264 Ugly Number II 70
265 Paint House II 60
266 Palindrome Permutation 100
267 Palindrome Permutation II 80 典型，多看两遍
268 Missing Number 100
269 Alien Dictionary 70 这题要多做几遍
270 Closest Binary Search Tree Value 90
271 Encode and Decode Strings 65 思路巧妙，多看几遍
272 Closest Binary Search Tree Value II 60 这题非常值得多做几遍，几种写法都试试
273 Integer to English Words 75 多做几遍，做到bug free
274 H-Index 80
275 H-Index II 75
277 Find the Celebrity 100
278 First Bad Version 100
279 Perfect Squares 95
280 Wiggle Sort 80 思路巧妙，多看两遍
281 Zigzag Iterator 85 多做三遍，考虑扩展到k的情况
282 Expression Add Operators 50
283 Move Zeroes 100
284 Peeking Iterator 100
285 Inorder Successor in BST 70 这道题有意思，要多做几遍
286 Walls and Gates 70 多看两遍
287 Find the Duplicate Number
288 Unique Word Abbreviation 70 这题不难，多做两遍，题目意思容易理解错
289 Game of Life 70
293 Flip Game 90
294 Flip Game II 90
295 Find Median from Data Stream
297 Serialize and Deserialize Binary Tree 80 好题目，多做做，递归的非递归的
298 Binary Tree Longest Consecutive Sequence 70 多做三遍，尽可能简洁
299 猜数字游戏 两次遍历，一次遍历
300 Longest Increasing Subsequence
301 Remove Invalid Parentheses 70 比较难，多做几遍
302 Smallest Rectangle Enclosing Black Pixels
303 Range Sum Query - Immutable 100
304 Range Sum Query 2D - Immutable 65
305 Number of Islands II 70 这题多做几遍，经典的UF
307 Range Sum Query - Mutable 70 和#303, #304, #308定要多做几遍，掌握BIT
308 Range Sum Query 2D - Mutable 70
309 Best Time to Buy and Sell Stock with Cooldown
310 Minimum Height Trees 60 这题多做几遍
311 Sparse Matrix Multiplication 80
312 Burst Balloons 60
313 Super Ugly Number
314 Binary Tree Vertical Order Traversal 80
315 Count of Smaller Numbers After Self 60
316 去除重复字母 70
317 Shortest Distance from All Buildings 75 典型的bfs，多做两遍
319 Bulb Switcher 90
320 Generalized Abbreviation 70 这题是典型的back tracking，多做几遍
322 Coin Change 80
323 Number of Connected Components in an Undirected Graph 90 典型的图，多看两遍
324 Wiggle Sort II 60
325 Maximum Size Subarray Sum Equals k 75 这题思路有意思，多做几遍
328 Odd Even Linked List 90
329 Longest Increasing Path in a Matrix 70 这题要多做几遍
332 Reconstruct Itinerary
333 Largest BST Subtree 50 这道题虽然不难，但是折腾了很久，一定要多做
334 Increasing Triplet Subsequence 75
335 Self Crossing 80
336 Palindrome Pairs
337 House Robber III 70 建议再做两遍
339 Nested List Weight Sum
340 Longest Substring with At Most K Distinct Characters 80 和#159类似
341 Flatten Nested List Iterator 75 这题有点意思，多做两遍
344 Reverse String 100
345 Reverse Vowels of a String 100
346 Moving Average from Data Stream 95
347 Top K Frequent Elements 85
349 Intersection of Two Arrays
350 Intersection of Two Arrays II
351 Android Unlock Patterns 70 这题多做几遍
357 Count Numbers with Unique Digits
358 Rearrange String k Distance Apart
359 Logger Rate Limiter 100 这题如果不考虑空间消耗的话其实很简单
361 Bomb Enemy 65 这题多做几遍，开始没思路
364 Nested List Weight Sum II
366 Find Leaves of Binary Tree 60 这道题刚开始还没思路
367 Valid Perfect Square
369 Plus One Linked List 100
370 Range Addition 80
373 Find K Pairs with Smallest Sums
374 Guess Number Higher or Lower 100
375 Guess Number Higher or Lower II 60
377 Combination Sum IV 65
378 Kth Smallest Element in a Sorted Matrix
380 Insert Delete GetRandom O(1) 75 这道题很有意思，多做几遍
381 Insert Delete GetRandom O(1) - Duplicates allowed
382 Linked List Random Node
384 Shuffle an Array 75
387 First Unique Character in a String 100
388 Longest Absolute File Path 65 其实不难，乍看没思路，多做几遍
391 Perfect Rectangle 70 这题很trick，多做两遍
通过 392 判断子序列 esay 贪心算法/DP算法 DP算法：不建议使用，纯粹学习思想
393 UTF-8 Validation 60 错了很多次，多做几遍
394 Decode String 75 这题容易错，多做四遍
395 Longest Substring with At Least K Repeating Characters 65
398 Random Pick Index 80
399 Evaluate Division 60 这题多做几遍
401 Binary Watch
404 Sum of Left Leaves 80
406 根据身高重建队列 60 这题开始没思路，多做几遍
407 Trapping Rain Water II
408 Valid Word Abbreviation 80 多做两遍
409 Longest Palindrome
410 Split Array Largest Sum
412 Fizz Buzz 100
413 Third Maximum Number 80
418 Sentence Screen Fitting 65 这题思路巧妙，多做几遍，常规思路超时
422 Valid Word Square 90
425 Word Squares 70 这题很典型，多做几遍
436 Find Right Interval
437 Path Sum III 60 这道题错了很多遍，要重点关注
438 Find All Anagrams in a String 75 这道题非常经典，最优解法需要多做几遍，保证once bug free
442 Find All Duplicates in an Array 80
445 Add Two Numbers II 80
448 Find All Numbers Disappeared in an Array 80
449 Serialize and Deserialize BST 90 和#297一样
通过 450 Delete Node in a BST 60 这题非常经典，值得多做十遍
451 Sort Characters By Frequency
通过 455 分发饼干 esay 贪心算法 贪心算法
458 可怜的小猪 Hard
459 Repeated Substring Pattern
477 Total Hamming Distance
480 Sliding Window Median 70
482 License Key Formatting 90
483 Smallest Good Base
485 Max Consecutive Ones 100
487 Max Consecutive Ones II 80
501 Find Mode in Binary Search Tree 70 不难，容易错，多做两次
508 Most Frequent Subtree Sum
513 Find Bottom Left Tree Value 100
515 Find Largest Value in Each Tree Row 100
524 Longest Word in Dictionary through Deleting
526 Beautiful Arrangement 80
535 Encode and Decode TinyURL 100
538 Convert BST to Greater Tree 100
541 Reverse String II 100
543 Diameter of Binary Tree 80 这题易错
547 Friend Circles 70
557 Reverse Words in a String III 100
560 Subarray Sum Equals K 70
563 Binary Tree Tilt 90
564 Find the Closest Palindrome 80 此题暴力法即可
572 Subtree of Another Tree 80
606 Construct String from Binary Tree 90
617 Merge Two Binary Trees 100 很简单
621 Task Scheduler 70
637 Average of Levels in Binary Tree 100
652 Find Duplicate Subtrees 70 开始还没思路
653 Two Sum IV - Input is a BST 90
654 Maximum Binary Tree 100
669 Trim a Binary Search Tree 100
681 Next Closest Time 80 这题多做几遍
683 K Empty Slots 80
684 Redundant Connection
687 Longest Univalue Path 70
695 Max Area of Island 100
小根堆解法待做 703 数据流中第K大元素 medium 优先级队列解法/小根堆解法 优先级队列解法/小根堆解法
771 Jewels and Stones 100
814 Binary Tree Pruning 80
819 Most Common Word 85
843 Guess the Word 90
844 Backspace String Compare 100
849 Maximize Distance to Closest Person 80
857 Minimum Cost to Hire K Workers 70
871 最低加油次数 80
872 Leaf-Similar Trees 80
889 Construct Binary Tree from Preorder and Postorder Traversal 80
904 Fruit Into Baskets 90
929 Unique Email Addresses 90

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