Common Beginner Mistakes

Concepts: pyDPMistakes, pyBaseCase, pyArraySizing

Most DP bugs fall into five categories. Experienced interviewers have seen all of them hundreds of times. Knowing these mistakes before you code is what separates the candidate who submits and passes from the candidate who submits, gets a wrong answer, and spends 10 minutes debugging. Here they are, with concrete examples of each. Mistake 1: Circular Dependency in Bottom-Up Bottom-up DP requires filling the table in an order where every dependency is already computed when you need it. For 1D DP, left-to-right is almost always correct. For 2D DP (coming in the intermediate lesson), the order is more subtle. The circular dependency error happens when dp[i] depends on dp[j] where j > i but you are iterating forward. The symptom is that your table contains uninitialized values when you try to