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artemkorsakov's solution

to Wordy in the C# Track

Published at Apr 21 2019 · 0 comments
Instructions
Test suite
Solution

Parse and evaluate simple math word problems returning the answer as an integer.

Iteration 0 — Numbers

Problems with no operations simply evaluate to the number given.

What is 5?

Evaluates to 5.

Iteration 1 — Addition

Add two numbers together.

What is 5 plus 13?

Evaluates to 18.

Handle large numbers and negative numbers.

Iteration 2 — Subtraction, Multiplication and Division

Now, perform the other three operations.

What is 7 minus 5?

2

What is 6 multiplied by 4?

24

What is 25 divided by 5?

5

Iteration 3 — Multiple Operations

Handle a set of operations, in sequence.

Since these are verbal word problems, evaluate the expression from left-to-right, ignoring the typical order of operations.

What is 5 plus 13 plus 6?

24

What is 3 plus 2 multiplied by 3?

15 (i.e. not 9)

Iteration 4 — Errors

The parser should reject:

  • Unsupported operations ("What is 52 cubed?")
  • Non-math questions ("Who is the President of the United States")
  • Word problems with invalid syntax ("What is 1 plus plus 2?")

Bonus — Exponentials

If you'd like, handle exponentials.

What is 2 raised to the 5th power?

32

Hints

  • To parse the text, you could try to use the Sprache library. You can also find a good tutorial here.

Running the tests

To run the tests, run the command dotnet test from within the exercise directory.

Initially, only the first test will be enabled. This is to encourage you to solve the exercise one step at a time. Once you get the first test passing, remove the Skip property from the next test and work on getting that test passing. Once none of the tests are skipped and they are all passing, you can submit your solution using exercism submit Wordy.cs

Further information

For more detailed information about the C# track, including how to get help if you're having trouble, please visit the exercism.io C# language page.

Source

Inspired by one of the generated questions in the Extreme Startup game. https://github.com/rchatley/extreme_startup

WordyTest.cs

// This file was auto-generated based on version 1.5.0 of the canonical data.

using System;
using Xunit;

public class WordyTest
{
    [Fact]
    public void Just_a_number()
    {
        Assert.Equal(5, Wordy.Answer("What is 5?"));
    }

    [Fact(Skip = "Remove to run test")]
    public void Addition()
    {
        Assert.Equal(2, Wordy.Answer("What is 1 plus 1?"));
    }

    [Fact(Skip = "Remove to run test")]
    public void More_addition()
    {
        Assert.Equal(55, Wordy.Answer("What is 53 plus 2?"));
    }

    [Fact(Skip = "Remove to run test")]
    public void Addition_with_negative_numbers()
    {
        Assert.Equal(-11, Wordy.Answer("What is -1 plus -10?"));
    }

    [Fact(Skip = "Remove to run test")]
    public void Large_addition()
    {
        Assert.Equal(45801, Wordy.Answer("What is 123 plus 45678?"));
    }

    [Fact(Skip = "Remove to run test")]
    public void Subtraction()
    {
        Assert.Equal(16, Wordy.Answer("What is 4 minus -12?"));
    }

    [Fact(Skip = "Remove to run test")]
    public void Multiplication()
    {
        Assert.Equal(-75, Wordy.Answer("What is -3 multiplied by 25?"));
    }

    [Fact(Skip = "Remove to run test")]
    public void Division()
    {
        Assert.Equal(-11, Wordy.Answer("What is 33 divided by -3?"));
    }

    [Fact(Skip = "Remove to run test")]
    public void Multiple_additions()
    {
        Assert.Equal(3, Wordy.Answer("What is 1 plus 1 plus 1?"));
    }

    [Fact(Skip = "Remove to run test")]
    public void Addition_and_subtraction()
    {
        Assert.Equal(8, Wordy.Answer("What is 1 plus 5 minus -2?"));
    }

    [Fact(Skip = "Remove to run test")]
    public void Multiple_subtraction()
    {
        Assert.Equal(3, Wordy.Answer("What is 20 minus 4 minus 13?"));
    }

    [Fact(Skip = "Remove to run test")]
    public void Subtraction_then_addition()
    {
        Assert.Equal(14, Wordy.Answer("What is 17 minus 6 plus 3?"));
    }

    [Fact(Skip = "Remove to run test")]
    public void Multiple_multiplication()
    {
        Assert.Equal(-12, Wordy.Answer("What is 2 multiplied by -2 multiplied by 3?"));
    }

    [Fact(Skip = "Remove to run test")]
    public void Addition_and_multiplication()
    {
        Assert.Equal(-8, Wordy.Answer("What is -3 plus 7 multiplied by -2?"));
    }

    [Fact(Skip = "Remove to run test")]
    public void Multiple_division()
    {
        Assert.Equal(2, Wordy.Answer("What is -12 divided by 2 divided by -3?"));
    }

    [Fact(Skip = "Remove to run test")]
    public void Unknown_operation()
    {
        Assert.Throws<ArgumentException>(() => Wordy.Answer("What is 52 cubed?"));
    }

    [Fact(Skip = "Remove to run test")]
    public void Non_math_question()
    {
        Assert.Throws<ArgumentException>(() => Wordy.Answer("Who is the President of the United States?"));
    }

    [Fact(Skip = "Remove to run test")]
    public void Reject_problem_missing_an_operand()
    {
        Assert.Throws<ArgumentException>(() => Wordy.Answer("What is 1 plus?"));
    }

    [Fact(Skip = "Remove to run test")]
    public void Reject_problem_with_no_operands_or_operators()
    {
        Assert.Throws<ArgumentException>(() => Wordy.Answer("What is?"));
    }

    [Fact(Skip = "Remove to run test")]
    public void Reject_two_operations_in_a_row()
    {
        Assert.Throws<ArgumentException>(() => Wordy.Answer("What is 1 plus plus 2?"));
    }

    [Fact(Skip = "Remove to run test")]
    public void Reject_two_numbers_in_a_row()
    {
        Assert.Throws<ArgumentException>(() => Wordy.Answer("What is 1 plus 2 1?"));
    }

    [Fact(Skip = "Remove to run test")]
    public void Reject_postfix_notation()
    {
        Assert.Throws<ArgumentException>(() => Wordy.Answer("What is 1 2 plus?"));
    }

    [Fact(Skip = "Remove to run test")]
    public void Reject_prefix_notation()
    {
        Assert.Throws<ArgumentException>(() => Wordy.Answer("What is plus 1 2?"));
    }
}
using System;
using System.Text.RegularExpressions;

public static class Wordy
{
    private static readonly Regex regexNumber = new Regex("-?\\d+");
    private static readonly Regex regexInitialNumber = new Regex("What is " + regexNumber);
    private static readonly Regex regexAddition = new Regex(" plus " + regexNumber);
    private static readonly Regex regexSubtraction = new Regex(" minus " + regexNumber);
    private static readonly Regex regexMultiplication = new Regex(" multiplied by " + regexNumber);
    private static readonly Regex regexDivision = new Regex(" divided by " + regexNumber);
    private static readonly Regex regexPower = new Regex(" raised to the \\d+[a-z]{2} power");
    private static readonly Regex regexMembers = new Regex("(" + regexAddition + "|" + regexSubtraction + "|" + regexMultiplication + "|" + regexDivision + "|" + regexPower + ")");
    private static readonly Regex regexAll = new Regex("^" + regexInitialNumber + regexMembers + "*\\?$");

    public static int Answer(string question)
    {
        if (!regexAll.IsMatch(question))
        {
            throw new ArgumentException("I'm sorry, I don't understand the question!");
        }

        int result = GetInitial(question);
        foreach (Match match in regexMembers.Matches(question))
        {
            result = result.Solve(match.Value);
        }
        return result;
    }

    private static int GetInitial(string input) => GetNumber(regexInitialNumber.Match(input).Value);

    private static int Solve(this int result, string input) => regexAddition.IsMatch(input)
            ? result + GetNumber(regexAddition.Match(input).Value)
            : regexSubtraction.IsMatch(input)
            ? result - GetNumber(regexSubtraction.Match(input).Value)
            : regexMultiplication.IsMatch(input)
            ? result * GetNumber(regexMultiplication.Match(input).Value)
            : regexDivision.IsMatch(input)
            ? result / GetNumber(regexDivision.Match(input).Value)
            : regexPower.IsMatch(input)
            ? (int)Math.Pow(result, GetNumber(regexPower.Match(input).Value))
            : result;

    private static int GetNumber(string input) => int.Parse(regexNumber.Match(input).Value);
}

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