chapter 4: stacks

Author: loiane

src/04-stack/03-base-converter-examples.ts

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+// src/04-stack/03-base-converter-examples.ts
+
+import decimalToBinary from './decimal-to-binary';
+import { decimalToBase, decimalToBase64 } from './decimal-to-base';
+
+// Decimal to binary
+console.log(decimalToBinary(0)); // 0
+console.log(decimalToBinary(1)); // 1
+console.log(decimalToBinary(2)); // 10
+console.log(decimalToBinary(13)); // 1101
+console.log(decimalToBinary(233)); // 11101001
+console.log(decimalToBinary(10)); // 1010
+console.log(decimalToBinary(1000)); // 1111101000
+
+// Decimal to base
+console.log(decimalToBase(100345, 2)); // 11000011111111001 
+console.log(decimalToBase(100345, 8)); // 303771 
+console.log(decimalToBase(100345, 16)); // 187F9 
+console.log(decimalToBase(100345, 35)); // 2BW0 
+
+// Decimal to base 64
+console.log(decimalToBase64(100345, 64)); // Yf5=
+
+// to see the output of this file use the command: npx ts-node src/04-stack/03-base-converter-examples.js

src/04-stack/decimal-to-base.ts

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+// src/04-stack/decimal-to-base.js
+
+import Stack from './stack';
+
+/**
+ * Converts a decimal number to a given base
+ * @param {number} decimalNumber - decimal number to be converted
+ * @param {number} base - base to convert the decimal number to
+ * @returns {string} base representation of the decimal number
+ */
+function decimalToBase(decimalNumber: number, base : number) {
+
+  if (base < 2 || base > 36) {
+    throw new Error('Base must be between 2 and 36');
+  }
+
+  const digits = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ'; // Digits for base 36
+  const remainderStack = new Stack<number>();
+  let baseString = '';
+
+  while (decimalNumber > 0) {
+    const remainder = Math.floor(decimalNumber % base);
+    remainderStack.push(remainder);
+    decimalNumber = Math.floor(decimalNumber / base);
+  }
+
+  while (!remainderStack.isEmpty()) {
+    baseString += digits[remainderStack.pop()]; // Use digit mapping
+  }
+
+  return baseString;
+}
+
+/**
+ * Converts a decimal number to a given base
+ * @param {number} decimalNumber - decimal number to be converted (between 2 and 36 or 64)
+ * @param {number} base - base to convert the decimal number to
+ * @returns {string} base representation of the decimal number
+ */
+function decimalToBase64(decimalNumber: number, base: number) {
+  if (base < 2 || (base > 36 && base !== 64)) {
+    throw new Error('Base must be between 2 and 36 or 64');
+  }
+
+  const digits = base === 64 ?
+    'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/' :
+    '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ';
+
+  const remainderStack = new Stack<number>();
+  let baseString = '';
+
+  while (decimalNumber > 0) {
+    const remainder = Math.floor(decimalNumber % base);
+    remainderStack.push(remainder);
+    decimalNumber = Math.floor(decimalNumber / base);
+  }
+
+  while (!remainderStack.isEmpty()) {
+    baseString += digits[remainderStack.pop()];
+  }
+
+  // Handle padding for Base64 (if necessary)
+  /* Base64 encodes data in groups of 3 bytes (24 bits). 
+  Each group is represented by four Base64 characters (6 bits per character). 
+  If the input data length isn't divisible by 3, padding characters (=) are added to the end of the output 
+  to ensure that the total length is a multiple of 4. 
+  This is important for proper decoding of the Base64 string back to its original data. */
+  if (base === 64) {
+    while (baseString.length % 4 !== 0) {
+      baseString += '=';
+    }
+  }
+
+  return baseString;
+}
+
+export { decimalToBase, decimalToBase64 };

src/04-stack/decimal-to-binary.ts

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+// src/04-stack/decimal-to-binary.js
+
+import Stack from './stack';
+
+/**
+ * Converts a decimal number to binary
+ * @param {number} decimalNumber - decimal number to be converted
+ * @returns {string} binary representation of the decimal number
+ */
+function decimalToBinary(decimalNumber: number) {
+  const remainderStack = new Stack<number>();
+  let binaryString = '';
+
+  if (decimalNumber === 0) {
+    return '0';
+  }
+
+  while (decimalNumber > 0) { // {1}
+    const remainder = Math.floor(decimalNumber % 2); // {2}
+    remainderStack.push(remainder); // {3}
+    decimalNumber = Math.floor(decimalNumber / 2); // {4}
+  }
+
+  while (!remainderStack.isEmpty()) { // {5}
+    binaryString += remainderStack.pop().toString();
+  }
+
+  return binaryString;
+}
+
+export default decimalToBinary;