Basic of Recursion (Before start on Dynamic Programing)

Sonika | @Walmart | Frontend Developer | 11 Years

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Nov 21, 2024

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1D Dynamic Programming

Write a recursive function sumOfDigits that takes a positive integer n and returns the sum of its digits.

sumOfDigits(123); // Output: 6 (1 + 2 + 3)
sumOfDigits(456); // Output: 15 (4 + 5 + 6)
sumOfDigits(9);   // Output: 9

function sumOfDigits(n) {
  // Base case: If n is a single digit
  if (n < 10) {
    return n;
  }
  
  // Recursive case: Sum the last digit and recurse on the rest
  return (n % 10) + sumOfDigits(Math.floor(n / 10));
}

// Test cases
console.log(sumOfDigits(123)); // 6
console.log(sumOfDigits(456)); // 15
console.log(sumOfDigits(9));   // 9

Write a recursive function factorial to calculate the factorial of a number n.

factorial(5); // Output: 120 (5 * 4 * 3 * 2 * 1)
factorial(0); // Output: 1

function factorial(n) {
  if (n === 0) return 1; // Base case
  return n * factorial(n - 1); // Recursive case
}

console.log(factorial(5)); // 120
console.log(factorial(0)); // 1

Write a recursive function fibonacci to return the nth Fibonacci number.

fibonacci(5); // Output: 5 (0, 1, 1, 2, 3, 5)
fibonacci(7); // Output: 13

function fibonacci(n) {
  if (n === 0) return 0; // Base case 1
  if (n === 1) return 1; //…