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What is recursion and what is a base case?

Q: What is recursion and what is a base case?

**Intuition.** Recursion solves a problem by solving a *smaller version of the same problem* and combining the result. The **base case** is the smallest version you can answer directly — it stops the recursion. No base case (or one you never reach) means infinite recursion and a **stack overflow**. factorial(4) — call stack grows, then unwinds <text x="130" y="54" fill="cur

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recursion

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Factorial — recursive

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def factorial(n):
    if n <= 1:          # base case
        return 1
    return n * factorial(n - 1)   # recursive case

print(factorial(4))    # 24

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