日期：2019.5.20 - 2019.6.11
每日提交 pull requests 的截止时间（以 5 月 20 号为例）：推荐时间是 5 月 20 号晚上 12 点之前，最后截止时间是 5 月 21 号凌晨 2 点之前，以 GitHub 上显示的时间戳为准，超过最后截止时间视为未能按时完成提交，出现一次即挑战失败，扣除押金，移出 GitHub organization 和微信群。
使用方法：
1、将 https://github.com/cracklc/lc fork 到自己账户下
2、以 inengch 为例：
# 将 fork 后的仓库 clone 到本地
git clone https://github.com/inengch/lc
# 切换到目录
cd lc
# 复制模版文件夹 username 为自己的用户名文件夹，比如这里用户名是 inengch
cp -R username inengch
# 切换到自己的用户名文件夹
cd inengch
# 切换到当天的文件夹，这里以第 1 天为例
cd 01
# 将相应的文件修改为你所使用的语言的对应的扩展名，比如我使用 C++
mv permutations permutations.cc
# 将相应的在 lintcode 上提交通过的代码复制粘贴到对应的文件中，然后提交到自己的 GitHub 仓库，当天要求完成的 6 道题全都提交完成后发起 pull requests
Day 1
Permutations
Permutations II
Subsets
Subsets II
Implement strStr()
strStr II
Day 2
Classical Binary Search
Wood Cut
Copy Books
Divide Two Integers
Drop Eggs
Find Minimum in Rotated Sorted Array
Day 3
Find Peak Element
First Bad Version
First Position of Target
Find K Closest Elements
Maximum Average Subarray
Maximum Number in Mountain Sequence
Day 4
Search a 2D Matrix
Search a 2D Matrix II
Search for a Range
Search in Rotated Sorted Array
Smallest Rectangle Enclosing Black Pixels
Sqrt(x)
Day 5
Balanced Binary Tree
Binary Tree Inorder Traversal
Binary Tree Longest Consecutive Sequence
Binary Tree Longest Consecutive Sequence II
Binary Tree Maximum Path Sum
Binary Tree Paths
Day 6
Binary Tree Postorder Traversal
Binary Tree Preorder Traversal
Convert Binary Tree to Doubly Linked List
Flatten Binary Tree to Linked List
Inorder Successor in BST
Lowest Common Ancestor of a Binary Tree
Day 7
Lowest Common Ancestor II
Lowest Common Ancestor III
Maximum Depth of Binary Tree
Minimum Depth of Binary Tree
Minimum Subtree
Validate Binary Search Tree
Day 8
Binary Tree Level Order Traversal
Binary Tree Level Order Traversal II
Serialize and Deserialize Binary Tree
Binary Tree Zigzag Level Order Traversal
Build Post Office II
Clone Graph
Day 9
Course Schedule
Graph Valid Tree
Number of Islands
Number of Islands II
Sequence Reconstruction
Topological Sorting
Day 10
Word Ladder
Combination Sum
Combination Sum II
Next Permutation II
Next Permutation
Palindrome Permutation
Day 11
Palindrome Permutation II
Permutation Index
Permutation Index II
Previous Permutation
String Permutation
Word Break
Day 12
Word Break II
Word Ladder II
Copy List with Random Pointer
Insert into a Cyclic Sorted List
Intersection of Two Arrays
Intersection of Two Arrays II
Day 13
Linked List Cycle
Linked List Cycle II
Maximum Product Subarray
Maximum Subarray Difference
Maximum Subarray
Maximum Subarray II
Day 14
Maximum Subarray III
Median of two Sorted Arrays
Merge Sorted Array
Merge Two Sorted Arrays
Merge Two Sorted Lists
Partition List
Day 15
Reverse Nodes in k-Group
Sort List
Subarray Sum Closest
Subarray Sum
3Sum Closest
3Sum
Day 16
4Sum
Move Zeroes
Partition Array
Remove Duplicates from Sorted Array
Sort Colors
Sort Colors II
Day 17
Triangle Count
Two Sum
Two Sum II - Input array is sorted
Two Sum III - Data structure design
Two Sum IV - Input is a BST
Valid Palindrome
Day 18
Decode String
Flatten 2D Vector
Flatten Nested List Iterator
Hash Function
Heapify
Implement Stack
Day 19
K Closest Points
Kth Largest Element
LFU Cache
LRU Cache
Longest Consecutive Sequence
Merge K Sorted Arrays
Day 20
Merge K Sorted Lists
Nested List Weight Sum
Rehashing
Top K Frequent Words (Map Reduce)
Top k Largest Numbers
Top k Largest Numbers II
Day 21
Ugly Number II
Zigzag Iterator
Zigzag Iterator II
Climbing Stairs
Climbing Stairs II
Drop Eggs II
Day 22
Frog Jump
Jump Game
Jump Game II
Largest Divisible Subset
Longest Increasing Subsequence
Minimum Path Sum
Day 23
Perfect Squares
Russian Doll Envelopes
Triangle
Unique Paths
Unique Paths II
Unique Paths III