My mistakes

Every mistake you make in a drill or mock paper belongs in your own mistakes log on My progress, with the fix. It's saved in your browser. Before the midterm, reread it and redo every row.

Classic beginner traps (watch for these)Copy Anchor Link

These are common errors. If you make one, add it to your mistakes log on My progress.

• Writing $\log(a+b) = \log a + \log b$. Wrong: the product rule is $\log(ab) = \log a + \log b$.
• Counting a for i = 1 to n loop header as $n$ checks. It runs $n+1$ times (the last check fails).
• Choosing $n_0$ before $c$ in a Big-O proof and then contradicting myself. Pick $c$, then the $n_0$ that makes it work.
• In induction, assuming the statement for $n$ and calling that the proof. You assume $n-1$ (or $k$) and prove $n$ (or $k+1$).
• Loop invariant that is true but useless at termination. It must say something that gives the answer when the loop stops.
• Recursion tree: forgetting the leaf level or getting the number of levels wrong. For halving, it's $\log_2 n + 1$ levels.