5. Recursion

Recursion fundamentals

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Base case + smaller problem

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Every recursive function needs a base case that stops the chain, and a recursive case that moves toward it.

The call stack stores frames. Too deep → stack overflow.

Classic: factorial, Fibonacci (naive is slow), tree DFS.

int fact(int n) {
  if (n <= 1) return 1;
  return n * fact(n - 1);
}

Check 2

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Without a base case, recursion typically

Fill in 3

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Try it 4

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Recursive factorial.

main.cpp

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Program input (stdin)

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Assignment 5

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Write int sumTo(int n) that returns 1+...+n recursively. Read n and print sumTo(n).

main.cpp

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