Problem

The United States uses the imperial system of weights and measures, which means that there are many different, seemingly arbitrary units to measure distance. There are 12 inches in a foot, 3 feet in a yard, 22 yards in a chain, and so on.

Create a data structure that can efficiently convert a certain quantity of one unit to the correct amount of any other unit. You should also allow for additional units to be added to the system.

Solution

To solve this problem, we can create a data structure that captures the relationships between different units and allows efficient conversion between them.

Method 1 - Using Hashmap

This class will store conversion factors between different units in a map and provide methods to convert between units and add new units.

  • We use a HashMap to store conversion factors from different units to a base unit (inches in this case).
  • The key in the map is the unit name (e.g., “inch”, “foot”), and the value is the conversion factor to inches.

Code

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52

public class ImperialUnitConverter {
    // Map to store conversion factors for each unit to a base unit (e.g., inches).
    private Map < String,
    Double > conversionFactors;

    public ImperialUnitConverter() {
        conversionFactors = new HashMap<>();

        // Initialize with some known conversions
        addUnit("inch", 1.0);
        addUnit("foot", 12.0); // 1 foot = 12 inches
        addUnit("yard", 36.0); // 1 yard = 3 feet = 36 inches
        addUnit("chain", 792.0); // 1 chain = 22 yards = 792 inches
    }

    public void addUnit(String unit, double factorToInch) {
        conversionFactors.put(unit, factorToInch);
    }

    public double convert(double quantity, String fromUnit, String toUnit) {
        if (!conversionFactors.containsKey(fromUnit) || !conversionFactors.containsKey(toUnit)) {
            throw new IllegalArgumentException("Unknown unit: " + fromUnit + " or " + toUnit);
        }

        double factorFrom = conversionFactors.get(fromUnit);
        double factorTo = conversionFactors.get(toUnit);

        // Convert the quantity to the base unit (inches) first, then to the target unit
        double quantityInInches = quantity * factorFrom;
        return quantityInInches / factorTo;
    }

    public static void main(String[] args) {
        ImperialUnitConverter converter = new ImperialUnitConverter();

        // Examples of conversion
        double feetToYards = converter.convert(6, "foot", "yard"); // 6 feet to yards
        System.out.println("6 feet is " + feetToYards + " yards");

        double yardsToChains = converter.convert(44, "yard", "chain"); // 44 yards to chains
        System.out.println("44 yards is " + yardsToChains + " chains");

        // Adding a new unit and converting
        converter.addUnit("mile", 63360.0); // 1 mile = 63360 inches

        double milesToInches = converter.convert(1, "mile", "inch"); // 1 mile to inches
        System.out.println("1 mile is " + milesToInches + " inches");

        double chainsToMiles = converter.convert(88, "chain", "mile"); // 88 chains to miles
        System.out.println("88 chains is " + chainsToMiles + " miles");
    }
}