# glennj's solution

## to Wordy in the Java Track

Published at Jan 13 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.

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)

## Bonus — Exponentials

If you'd like, handle exponentials.

What is 2 raised to the 5th power?

32

# Running the tests

You can run all the tests for an exercise by entering

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

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

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

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

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

@Ignore("Remove to run test")
@Test
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
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
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 testInvalidQuestionFormat() {
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?");
}

}``````
``````import java.util.HashMap;
import java.util.Map;
import java.util.function.IntBinaryOperator;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.stream.Collectors;

class WordProblemSolver {
private static final Map<String, IntBinaryOperator> calculator;
static {
calculator = new HashMap<>();
calculator.put("plus",          (a, b) -> a + b);
calculator.put("minus",         (a, b) -> a - b);
calculator.put("multiplied by", (a, b) -> a * b);
calculator.put("divided by",    (a, b) -> a / b);
}

private static final Pattern EXPR;
static {
String integer = "-?\\d+";
String operator = calculator.keySet().stream().collect(Collectors.joining("|"));
String pattern = String.format("(%s)\\s+(%s)\\s+(%s)", integer, operator, integer);
EXPR = Pattern.compile(pattern);
}

public int solve(String question) {
question = question.replaceFirst("^What is ", "").replaceFirst("\\?\$", "");

Matcher m = EXPR.matcher(question);
while (m.find()) {
int ans = calculator
.get(m.group(2))
.applyAsInt(
Integer.parseInt(m.group(1)),
Integer.parseInt(m.group(3))
);
question = m.replaceFirst(String.valueOf(ans));
m = EXPR.matcher(question);
}

// at this point, we could have a unary operator dispatcher
// to handle things like "-5 absolute value" or "53 cubed"

try {
return Integer.parseInt(question);
} catch (NumberFormatException e) {
throw new IllegalArgumentException("I'm sorry, I don't understand the question!");
}
}
}``````