Pattern visualizer
Factorial & the Call Stack
Recursion solves a problem by calling itself on a smaller input and trusting that smaller answer. The hidden machinery is the call stack: every call pushes a frame holding its paused work, and answers flow back as frames pop in reverse order. Each cell here is one stack frame — watch them pile up to the base case, then unwind carrying the products home. Animated on: Compute factorial(5) = 5 x 4 x 3 x 2 x 1 recursively, watching the call stack grow to depth 5 and then unwind..
Frames push down to the base case, answers unwind back up
time O(n)space O(n)step 1 / 11
f(5)
[0]line 6
Call factorial(5). A frame for it is pushed onto the call stack — the stack is how the program remembers who is waiting for whom.
Pseudocode
1FUNCTION factorial(n):2 IF n == 1:3 RETURN 1 (base case — stops the descent)4 (pause here until the smaller call answers)5 RETURN n * factorial(n - 1)6call factorial(5)
← / → step · space play · Home restart