Change project structure to a Maven Java project + Refactor (#2816)

src/main/java/com/thealgorithms/conversions/AnyBaseToAnyBase.java

@@ -0,0 +1,145 @@
+package com.thealgorithms.conversions;
+
+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, 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 2017.10.10
+ */
+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;
+
+    public static void main(String[] args) {
+        Scanner in = new Scanner(System.in);
+        String n;
+        int b1, b2;
+        while (true) {
+            try {
+                System.out.print("Enter number: ");
+                n = in.next();
+                System.out.print(
+                        "Enter beginning base (between " + MINIMUM_BASE + " and " + MAXIMUM_BASE + "): ");
+                b1 = in.nextInt();
+                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.");
+                in.next();
+            }
+        }
+        System.out.println(base2base(n, b1, b2));
+        in.close();
+    }
+
+    /**
+     * 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.
+     *
+     * @param n The integer to be converted.
+     * @param b1 Beginning base.
+     * @param b2 End base.
+     * @return n in base b2.
+     */
+    public static String base2base(String n, int b1, int b2) {
+        // Declare variables: decimal value of n,
+        // character of base b1, character of base b2,
+        // and the string that will be returned.
+        int decimalValue = 0, charB2;
+        char charB1;
+        String output = "";
+        // Go through every character of n
+        for (int i = 0; i < n.length(); i++) {
+            // store the character in charB1
+            charB1 = n.charAt(i);
+            // if it is a non-number, convert it to a decimal value >9 and store it in charB2
+            if (charB1 >= 'A' && charB1 <= 'Z') {
+                charB2 = 10 + (charB1 - 'A');
+            } // Else, store the integer value in charB2
+            else {
+                charB2 = charB1 - '0';
+            }
+            // Convert the digit to decimal and add it to the
+            // decimalValue of n
+            decimalValue = decimalValue * b1 + charB2;
+        }
+
+        // Converting the decimal value to base b2:
+        // A number is converted from decimal to another base
+        // by continuously dividing by the base and recording
+        // the remainder until the quotient is zero. The number in the
+        // new base is the remainders, with the last remainder
+        // being the left-most digit.
+        if (0 == decimalValue) {
+            return "0";
+        }
+        // While the quotient is NOT zero:
+        while (decimalValue != 0) {
+            // If the remainder is a digit < 10, simply add it to
+            // the left side of the new number.
+            if (decimalValue % b2 < 10) {
+                output = Integer.toString(decimalValue % b2) + output;
+            } // If the remainder is >= 10, add a character with the
+            // corresponding value to the new number. (A = 10, B = 11, C = 12, ...)
+            else {
+                output = (char) ((decimalValue % b2) + 55) + output;
+            }
+            // Divide by the new base again
+            decimalValue /= b2;
+        }
+        return output;
+    }
+}