Chapter 11 — Learning to Write in Recursive

Recursive mindset

Solve the current layer and trust recursion to solve the smaller problem

Repeatedly execute pattern

Do one action, then call the function with updated input

Extra parameter

Tracks progress through recursive calls

Index parameter

Tracks the current position in an array or string

Calculation recursion

Return current value combined with recursive result

Array sum recursion

First value plus sum of rest

Find x recursion

Check current index, otherwise recurse with index + 1

Top-down recursive thinking

Assume recursive call solves the smaller problem

Triangular number

N plus triangular_number(N - 1)

Unique paths base case

If rows == 1 or columns == 1, return 1

Unique paths recursive case

unique_paths(rows - 1, columns) + unique_paths(rows, columns - 1)

Anagram base case

One-character string returns itself

Anagram time

O(N!), because all arrangements are generate