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# mwpb's solution

## to Wordy in the Java Track

Published at Nov 18 2019 · 0 comments
Instructions
Test suite
Solution

#### Note:

This exercise has changed since this solution was written.

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

## Iteration 0 β Numbers

Problems with no operations simply evaluate to the number given.

What is 5?

Evaluates to 5.

## Iteration 1 β Addition

Add two numbers together.

What is 5 plus 13?

Evaluates to 18.

Handle large numbers and negative numbers.

## Iteration 2 β 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 β 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 β 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 β Exponentials

If you'd like, handle exponentials.

What is 2 raised to the 5th power?

32

## Setup

Go through the setup instructions for Java to install the necessary dependencies:

https://exercism.io/tracks/java/installation

# Running the tests

You can run all the tests for an exercise by entering the following in your terminal:

``````\$ gradle test
``````

Use `gradlew.bat` if you're on Windows

In the test suites all tests but the first have been skipped.

Once you get a test passing, you can enable the next one by removing the `@Ignore("Remove to run test")` annotation.

## Source

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

## Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

### WordProblemSolverTest.java

``````import org.junit.Ignore;
import org.junit.Rule;
import org.junit.Test;
import org.junit.Before;
import org.junit.rules.ExpectedException;

import static org.junit.Assert.assertEquals;

public class WordProblemSolverTest {

@Rule
public ExpectedException expectedException = ExpectedException.none();

WordProblemSolver solver;

@Before
public void setup() {
solver = new WordProblemSolver();
}

@Test
public void testJustANumber() {
assertEquals(5, solver.solve("What is 5?"));
}

@Ignore("Remove to run test")
@Test
public void testSingleAddition1() {
assertEquals(2, solver.solve("What is 1 plus 1?"));
}

@Ignore("Remove to run test")
@Test
public void testSingleAddition2() {
assertEquals(55, solver.solve("What is 53 plus 2?"));
}

@Ignore("Remove to run test")
@Test
public void testSingleAdditionWithNegativeNumbers() {
assertEquals(-11, solver.solve("What is -1 plus -10?"));
}

@Ignore("Remove to run test")
@Test
public void testSingleAdditionOfLargeNumbers() {
assertEquals(45801, solver.solve("What is 123 plus 45678?"));
}

@Ignore("Remove to run test")
@Test
public void testSingleSubtraction() {
assertEquals(16, solver.solve("What is 4 minus -12?"));
}

@Ignore("Remove to run test")
@Test
public void testSingleMultiplication() {
assertEquals(-75, solver.solve("What is -3 multiplied by 25?"));
}

@Ignore("Remove to run test")
@Test
public void testSingleDivision() {
assertEquals(-11, solver.solve("What is 33 divided by -3?"));
}

@Ignore("Remove to run test")
@Test
public void testMultipleAdditions() {
assertEquals(3, solver.solve("What is 1 plus 1 plus 1?"));
}

@Ignore("Remove to run test")
@Test
public void testAdditionThenSubtraction() {
assertEquals(8, solver.solve("What is 1 plus 5 minus -2?"));
}

@Ignore("Remove to run test")
@Test
public void testMultipleSubtractions() {
assertEquals(3, solver.solve("What is 20 minus 4 minus 13?"));
}

@Ignore("Remove to run test")
@Test
public void testSubtractionThenAddition() {
assertEquals(14, solver.solve("What is 17 minus 6 plus 3?"));
}

@Ignore("Remove to run test")
@Test
public void testMultipleMultiplications() {
assertEquals(-12, solver.solve("What is 2 multiplied by -2 multiplied by 3?"));
}

@Ignore("Remove to run test")
@Test
public void testAdditionThenMultiplication() {
assertEquals(-8, solver.solve("What is -3 plus 7 multiplied by -2?"));
}

@Ignore("Remove to run test")
@Test
public void testMultipleDivisions() {
assertEquals(2, solver.solve("What is -12 divided by 2 divided by -3?"));
}

@Ignore("Remove to run test")
@Test
public void testUnknownOperation() {
expectedException.expect(IllegalArgumentException.class);
expectedException.expectMessage("I'm sorry, I don't understand the question!");

solver.solve("What is 52 cubed?");
}

@Ignore("Remove to run test")
@Test
public void testNonMathQuestion() {
expectedException.expect(IllegalArgumentException.class);
expectedException.expectMessage("I'm sorry, I don't understand the question!");

// See https://en.wikipedia.org/wiki/President_of_the_United_States if you really need to know!
solver.solve("Who is the President of the United States?");
}

@Ignore("Remove to run test")
@Test
public void testMissingAnOperand() {
expectedException.expect(IllegalArgumentException.class);
expectedException.expectMessage("I'm sorry, I don't understand the question!");

solver.solve("What is 1 plus?");
}

@Ignore("Remove to run test")
@Test
public void testNoOperandsOrOperators() {
expectedException.expect(IllegalArgumentException.class);
expectedException.expectMessage("I'm sorry, I don't understand the question!");

solver.solve("What is?");
}

@Ignore("Remove to run test")
@Test
public void testTwoOperationsInARow() {
expectedException.expect(IllegalArgumentException.class);
expectedException.expectMessage("I'm sorry, I don't understand the question!");

solver.solve("What is 1 plus plus 2?");
}

@Ignore("Remove to run test")
@Test
public void testTwoNumbersAfterOperation() {
expectedException.expect(IllegalArgumentException.class);
expectedException.expectMessage("I'm sorry, I don't understand the question!");

solver.solve("What is 1 plus 2 1?");
}

@Ignore("Remove to run test")
@Test
public void testPostfixNotation() {
expectedException.expect(IllegalArgumentException.class);
expectedException.expectMessage("I'm sorry, I don't understand the question!");

solver.solve("What is 1 2 plus?");
}

@Ignore("Remove to run test")
@Test
public void testPrefixNotation() {
expectedException.expect(IllegalArgumentException.class);
expectedException.expectMessage("I'm sorry, I don't understand the question!");

solver.solve("What is plus 1 2?");
}
}``````
``````import java.util.*;
import java.util.stream.*;

class WordProblemSolver {

Iterator<String> it;

int getInt() {
if (!this.it.hasNext()) {
throw new IllegalArgumentException("I'm sorry, I don't understand the question!");
}
String word = this.it.next();
if (!word.matches("-?\\d+")) {
throw new IllegalArgumentException("I'm sorry, I don't understand the question!");
}
return Integer.parseInt(word);
}

String getString() {
if (!this.it.hasNext()) {
throw new IllegalArgumentException("I'm sorry, I don't understand the question!");
}
return this.it.next();
}

String getString(String expected) {
if (!this.it.hasNext()) {
throw new IllegalArgumentException("I'm sorry, I don't understand the question!");
}
String word = this.it.next();
if (!word.equals(expected)) {
throw new IllegalArgumentException("I'm sorry, I don't understand the question!");
}
return word;
}

void parseInput(String wordProblem) {
if (wordProblem.length() < 10 || !wordProblem.startsWith("What is ") || !wordProblem.endsWith("?")) {
throw new IllegalArgumentException("I'm sorry, I don't understand the question!");
}
String trimmed = wordProblem.substring(8, wordProblem.length()-1);
String[] words = trimmed.split(" ");
if (words.length == 0 || words.length == 2) {
throw new IllegalArgumentException("I'm sorry, I don't understand the question!");
}
this.it = Arrays.stream(words).iterator();
}

int solve(String wordProblem) {
this.parseInput(wordProblem);
int ans = this.getInt();
while (this.it.hasNext()) {
String word = this.it.next();
if (word.equals("plus")) {
ans += this.getInt();
} else if (word.equals("minus")) {
ans -= this.getInt();
} else if (word.equals("multiplied")) {
this.getString("by");
ans *= this.getInt();
} else if (word.equals("divided")) {
this.getString("by");
ans = ans / this.getInt();
} else {
throw new IllegalArgumentException("I'm sorry, I don't understand the question!");
}
}
return ans;
}
}``````