Common Recursion Mistakes

Four mistakes that trip up beginners:

$1.$ Missing base case. Your function calls itself forever until stack overflow.

$2.$ Base case never reached. Each call must move toward the base case. If power($2$, $n$) called power($2$, $n$+$1$), you'd recurse forever.

$3.$ Wrong return value. Forgetting to return the recursive result loses the answer.

$4.$ Modifying shared state. If your function changes a global variable, recursive calls can interfere with each other. When your recursive code crashes or gives wrong answers, check these four things first.