CS 70

Getting Help with Homework 4

Ask your Homework 4 questions here. Use the box at the bottom of this page. Your question is posted to this page for the class to see, under an animal name rather than your own—and if you would rather only the course staff saw it, there is a box to tick for that.

Course staff read this page. So do your classmates, and a classmate answering first is a good outcome rather than a failure of the system.

  • Goat speaking

    Meh. Why not just email somebody?

  • LHS Cow speaking

    Because one answer here reaches everyone with the same problem, and on this assignment a lot of people hit the same memory-management and maze-solving snags within an hour of each other.

  • Duck speaking

    So if my CoordVector is leaking, somebody else's probably is too?

  • LHS Cow speaking

    Almost certainly. That is exactly the kind of question that is worth asking in public.

Before you ask

  • Run valgrind and read the first error. On this assignment most bugs are memory bugs, and the first thing valgrind complains about is usually the real cause; later errors are often fallout.
  • make clean then make. If valgrind reports no line numbers, or your change seems to have no effect, a stale build is the usual reason.
  • Check the help pages — Using Valgrind, the CS 70 Testing Library, and Working With Makefiles.
  • If your question is about a lesson rather than the assignment, ask on that lesson's Key Points page instead, where it sits next to the material.

Asking a question we can actually answer

  • Push your code first. Commit, push, and say so — then whoever picks up your question can look at the real thing rather than at a description of it.
  • The exact command you ran—pasted, not summarised.
  • The exact output or error, in full, in a ``` code block. Compiler, linker, and valgrind output is long and the useful line is often not the last one, so paste all of it.
  • What you expected instead, and what you have already tried.

Things that go wrong on Homework 4 specifically

  • Memory leaks / invalid delete. Remember delete[] (not delete) for array allocations, and that every new[] needs exactly one matching delete[]. Say what valgrind reported and which method it points at.
  • Circular-buffer bugs in CoordVector. If offset_ doesn't wrap correctly in both directions, say what you pushed/popped and what came out.
  • A solver finds the goal but not the path. BFS must reconstruct the actual path, not just confirm reachability.
  • Makefile trouble. Paste your Makefile and the exact make output.
  • Your partner's copy works and yours doesn't. Usually one of you has not pulled the other's latest commits. Pull first, then say what still differs.

When a conversation would be faster

  • Ask in lab, especially for anything where someone looking at your screen beats a paragraph of description.
  • Come to grutoring or office hours for anything conceptual, or for the questions that are hard to phrase.
  • For anything personal, or about the course rather than the code, contact a professor directly.

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