LeetCode

Study notes for data structures & algorithms

Data Structures

Array

Rotate

1. 逆推
2. Reverse
3. Swap (主对角线, 分界线, 轴)

Linked List

常规手段

• dummy 作哨兵, cur 作游标
• 一直遍历（最长链表）, 每次遍历再进行空值判断

Reverse list

• pre, cur, post

Tree

Root-to-leaf

• int: a + b (choose a non-empty element between a and b)
• boolean: false (if root is null)
• void: return

Whether the node is empty

• (root) ? null : root

Stack and Queue

Circular Queue

• 根据 head 和 size 计算出 tail
• 循环: 对 n 取模

Hashtable

Two Sum

• 需要频繁访问 target 时，考虑采用哈希表

String

KMP

Graph

Bit Manipulation

Algorithms

Two Pointers

Two Sum

• 返回的是元素而非 index，可考虑排序 + 双指针

Sorting

Greedy

Binary Seach

Divide and Conquer

Searching

Dynamic Programming

Math

Add two numbers

• reverse
• carry : sum / n (n 进制)
• pop : sum % n (n 进制)

Missing number

• Gauss' Formula