Recursion Simple Problems - rohit120582sharma/Documentation GitHub Wiki

Power

Without tail call

function pow(base, power){
	// Base condition
	if(power <= 0){
		return 1;
	}
	// Change input and recursion
	return base * pow(base, power-1); //tail call === false
}

With tail call

function pow(base, power){
	if(power <= 0){
		return 1;
	}
	// Call helper function
	return helper(base, power, base); //tail call === true
}
function helper(base, power, num){
	// Base condition
	if(power === 1){
		return num;
	}
	// Change input and recursion
	return helper(base, power - 1, base * num);
}

Factorial

Write a function factorial which accepts a number and returns the factorial of that number. A factorial is the product of an integer and all the integers below it; e.g., factorial four (4!) is equal to 24, because 4 * 3 * 2 * 1 equals 24. factorial zero (0!) is always 1.

function factorial(num){
	// Base Case
	if(num <= 1){
		return 1;
	}

	// Change input and recursion
	return num * factorial(num-1);
}

Fibonacci

Write a recursive function called fib which accepts a number and returns the nth number in the Fibonacci sequence. Recall that the Fibonacci sequence is the sequence of whole numbers 1, 1, 2, 3, 5, 8, ... which starts with 1 and 1, and where every number thereafter is equal to the sum of the previous two numbers.

function fib(n){
	// Base Case
	if(n <= 2){
		return 1;
	}

	// Change input and recusrion
	return fib(n-1) + fib(n-2);
}
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