Very easily tricked.
See e.g. this wrong factorial implementation:<p>int fun(int n){<p>if (n==1 || n==2){<p><pre><code> return 1;
</code></pre>
}else{<p><pre><code> return fun(1) + fun(n-2);
</code></pre>
}<p>}<p>"The function recursively calls itself twice, with n-2 and 1 as arguments. This creates a binary tree with a depth of n, and each node has two children. Therefore, the total number of nodes in the tree is 2^n. Since each node represents a function call, the time complexity is O(2^n)."