算法面试之题目分类，按类型和规律刷题，事半功倍

算法面试过程中，题目类型多，数量大。大家都不可避免的会在LeetCode上进行训练。但问题是，题目杂，而且已经超过1000道题。全部刷完且掌握，不是一件容易的事情。那我们应该怎么办呢？找规律，总结才是制胜法宝。下面我们就来看看Grokking the Coding Interview: Patterns for Coding Questions的分类及每个类型的经典题目：

1. Pattern: Sliding window，滑动窗口类型

经典题目：
Maximum Sum Subarray of Size K (easy)
Smallest Subarray with a given sum (easy)
Longest Substring with K Distinct Characters (medium)
Fruits into Baskets (medium)
No-repeat Substring (hard)
Longest Substring with Same Letters after Replacement (hard)
Longest Subarray with Ones after Replacement (hard)

2. Pattern: two points, 双指针类型

经典题目：
Pair with Target Sum (easy)
Remove Duplicates (easy)
Squaring a Sorted Array (easy)
Triplet Sum to Zero (medium)
Triplet Sum Close to Target (medium)
Triplets with Smaller Sum (medium)
Subarrays with Product Less than a Target (medium)
Dutch National Flag Problem (medium)

3. Pattern: Fast & Slow pointers, 快慢指针类型

经典题目：
LinkedList Cycle (easy)
Start of LinkedList Cycle (medium)
Happy Number (medium)
Middle of the LinkedList (easy)

4. Pattern: Merge Intervals，区间合并类型

经典题目：
Merge Intervals (medium)
Insert Interval (medium)
Intervals Intersection (medium)
Conflicting Appointments (medium)

5. Pattern: Cyclic Sort，循环排序

经典题目：
Cyclic Sort (easy)
Find the Missing Number (easy)
Find all Missing Numbers (easy)
Find the Duplicate Number (easy)
Find all Duplicate Numbers (easy)

6. Pattern: In-place Reversal of a LinkedList，链表翻转

经典题目：
Reverse a LinkedList (easy)
Reverse a Sub-list (medium)
Reverse every K-element Sub-list (medium)

7. Pattern: Tree Breadth First Search，树上的BFS

经典题目：
Binary Tree Level Order Traversal (easy)
Reverse Level Order Traversal (easy)
Zigzag Traversal (medium)
Level Averages in a Binary Tree (easy)
Minimum Depth of a Binary Tree (easy)
Level Order Successor (easy)
Connect Level Order Siblings (medium)

8. Pattern: Tree Depth First Search，树上的DFS

经典题目：
Binary Tree Path Sum (easy)
All Paths for a Sum (medium)
Sum of Path Numbers (medium)
Path With Given Sequence (medium)
Count Paths for a Sum (medium)

9. Pattern: Two Heaps，双堆类型

经典题目：
Find the Median of a Number Stream (medium)
Sliding Window Median (hard)
Maximize Capital (hard)

10. Pattern: Subsets，子集类型，一般都是使用多重DFS

经典题目：
Subsets (easy)
Subsets With Duplicates (easy)
Permutations (medium)
String Permutations by changing case (medium)
Balanced Parentheses (hard)
Unique Generalized Abbreviations (hard)

11. Pattern: Modified Binary Search，改造过的二分

经典题目：
Order-agnostic Binary Search (easy)
Ceiling of a Number (medium)
Next Letter (medium)
Number Range (medium)
Search in a Sorted Infinite Array (medium)
Minimum Difference Element (medium)
Bitonic Array Maximum (easy)

12. Pattern: Top ‘K’ Elements，前K个系列

经典题目：
Top ‘K’ Numbers (easy)
Kth Smallest Number (easy)
‘K’ Closest Points to the Origin (easy)
Connect Ropes (easy)
Top ‘K’ Frequent Numbers (medium)
Frequency Sort (medium)
Kth Largest Number in a Stream (medium)
‘K’ Closest Numbers (medium)
Maximum Distinct Elements (medium)
Sum of Elements (medium)
Rearrange String (hard)

13. Pattern: K-way merge，多路归并

经典题目：
Merge K Sorted Lists (medium)
Kth Smallest Number in M Sorted Lists (Medium)
Kth Smallest Number in a Sorted Matrix (Hard)
Smallest Number Range (Hard)

14. Pattern: 0/1 Knapsack (Dynamic Programming)，0/1背包类型

经典题目：
0/1 Knapsack (medium)
Equal Subset Sum Partition (medium)
Subset Sum (medium)
Minimum Subset Sum Difference (hard)

15. Pattern: Topological Sort (Graph)，拓扑排序类型

经典题目：
Topological Sort (medium)
Tasks Scheduling (medium)
Tasks Scheduling Order (medium)
All Tasks Scheduling Orders (hard)
Alien Dictionary (hard)

大家好好练练这些题目，面试中遇到高等难度的题目，应该就能解得不错了。