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Add validForBase() and min/max base constants #183

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Oct 11, 2017
Merged

Add validForBase() and min/max base constants #183

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57 changes: 50 additions & 7 deletions Conversions/AnyBaseToAnyBase.java
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Original file line number Diff line number Diff line change
@@ -1,28 +1,48 @@
import java.util.Arrays;
import java.util.HashSet;
import java.util.InputMismatchException;
import java.util.Scanner;

/**
* Class for converting from any base to any other base, though it's unclear how digits greater than
* 36 would be represented in bases >36.
* Class for converting from "any" base to "any" other base, when "any" means from 2-36.
* Works by going from base 1 to decimal to base 2. Includes auxiliary method for
* determining whether a number is valid for a given base.
*
* @author Michael Rolland
* @version 2017.09.29
* @version 2017.10.10
*
*/
public class AnyBaseToAnyBase {

// Smallest and largest base you want to accept as valid input
static final int MINIMUM_BASE = 2;
static final int MAXIMUM_BASE = 36;

// Driver
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
System.out.print("Enter number: ");
String n = in.nextLine();
String n;
int b1=0,b2=0;
while (true) {
try {
System.out.print("Enter beginning base: ");
System.out.print("Enter number: ");
n = in.next();
System.out.print("Enter beginning base (between "+MINIMUM_BASE+" and "+MAXIMUM_BASE+"): ");
b1 = in.nextInt();
System.out.print("Enter end base: ");
if (b1 > MAXIMUM_BASE || b1 < MINIMUM_BASE) {
System.out.println("Invalid base!");
continue;
}
if (!validForBase(n, b1)) {
System.out.println("The number is invalid for this base!");
continue;
}
System.out.print("Enter end base (between "+MINIMUM_BASE+" and "+MAXIMUM_BASE+"): ");
b2 = in.nextInt();
if (b2 > MAXIMUM_BASE || b2 < MINIMUM_BASE) {
System.out.println("Invalid base!");
continue;
}
break;
} catch (InputMismatchException e) {
System.out.println("Invalid input.");
Expand All @@ -32,6 +52,29 @@ public static void main(String[] args) {
System.out.println(base2base(n, b1, b2));
}

/**
* Checks if a number (as a String) is valid for a given base.
*/
public static boolean validForBase(String n, int base) {
char[] validDigits = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E',
'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V',
'W', 'X', 'Y', 'Z'};
// digitsForBase contains all the valid digits for the base given
char[] digitsForBase = Arrays.copyOfRange(validDigits, 0, base);

// Convert character array into set for convenience of contains() method
HashSet<Character> digitsList = new HashSet();
for (int i=0; i<digitsForBase.length; i++)
digitsList.add(digitsForBase[i]);

// Check that every digit in n is within the list of valid digits for that base.
for (char c : n.toCharArray())
if (!digitsList.contains(c))
return false;

return true;
}

/**
* Method to convert any integer from base b1 to base b2. Works by converting from b1 to decimal,
* then decimal to b2.
Expand Down