Reach AI


So far you’ve been deep in the trenches of implementing a functional game that interacts with a user. Now, it’s time to pivot and think as the user of this game. Specifically, what kind of decisions should you make as a player of this game to get the best performance from the elevators?

NOTE: This part of the specification is tentative and subject to change up until the due date of the Core.

First Steps

Play through the game, and for each move you make, ask yourself why you decided to do the thing you did. What kind of rules come to mind?

Understanding the Metrics

What does it mean to be the “best” elevator? To answer this question, we will resort to defining a SatisfactionIndex. Make sure to read through and understand what each of these values represent. If you had to play the game trying to get the best possible values for these, what would you do?

The AI Move Framework

Among the functionality we’ve built for you, we’ve created the files AI.cpp and AI.h, which are provided with the same information that is provided to the Player via the terminal and should create valid Moves. For the reach, you will be responsible for implementing the functions in AI.cpp in such a way that gets good performance. More concretely, we will evaluate 2 things:

Implementation Considerations

You are encouraged to devise helper functions to aid you in writing the functions in AI.cpp; you can add these directly to AI.cpp when you submit. You are also permitted to include any libraries present in the C++11 standard template library, provided that you don’t have to modify your build process to get them to work. Do not edit AI.h. We should be able to run your code immediately when we make a project in XCode or Visual Studio.

Testing your AI

As always, it is imperative to test your code well. Elevators reach is different from the other 183 projects in that your grade is determined by performance for AI.cpp. So, now your tests are not only concerned with correctness, but also with benchmarking the power of your AI. You should be constantly testing whether your AI performs well on different inputs.

There are two ways to test your AI:

Input Files

A description of input files and how to use them are found on this page: Input Files


You will submit your files to the autograder for the Reach. You will submit AI.cpp to the autograder.


Your AI, the functions in AI.cpp, will be graded by the performance of your AI with a variety of input events:

A Note

This section may seem fairly open-ended, and you may feel slightly confused about what your AI is responsible for doing. This is by design. Often times, real-world “specs” are vague about a lot of implementation details. It becomes the responsibility of the programmer to think about the problem and decide on what’s best for the project. Think! Discuss with your groupmates! Think some more! Try things! Fail! Try again! Have fun!


The functions in AI.h are not part of a class.

You will be writing the implementations for the following functions:


* Requires: buildingState is a valid state representing the current building
* Modifies: Nothing
* Effects:  Returns a string that represents the decision the AI makes 
*           given the current state of the building, which it reads 
*           from buildingState.
*           The string should share the exact format as a 
*           human player's move input.
string getAIMoveString(const BuildingState& buildingState);

This function should determine the next move when playing the game.


* Requires: buildingState is a valid state representing the current building
*           move is a pickup move that was generated by getAIMoveString()
*           floorToPickup represents the floor the pickup move occurred.
* Modifies: Nothing
* Effects:  Returns a string representing which people indices 
*           should be picked up. The string should share the exact format 
*           as a human player's pickup list input.
string getAIPickupList(const Move& move, const BuildingState& buildingState, const Floor& floorToPickup);

This function should determine the pickup list based on the move and state of the building and floor.

An example pickupList: "0135"

“I choose the people at indices 0, 1, 3, and 5 to pickup”

A pickupList is valid if it meets the following conditions:

  1. There are no duplicate indices present in pickupList
  2. Each element of pickupList is a non-negative digit
  3. The length of the pickupList is less than or equal to the capacity of an elevator
  4. The maximum value pointed to by an index of pickupList must be strictly less than the number of people on the floor pointed to by pickupFloorNum
  5. Each person represented by an index in pickupList must be going in the same direction relative to pickupFloorNum