The ultimate guide to recursion interviews with strategies developed by FAANG engineers. Practice with real-world interview questions, detailed explanations, and visualizations to prep faster.

If you’ve got an interview coming up and want to brush up on your knowledge, or if you’ve ever struggled with solving coding problems using recursion, you'll find this course helpful.
 
You’ll start with the basics of what recursion is and why it’s important before diving into what it looks like in practice. You’ll see how recursion can help you solve a variety of different math, string, and data structure problems by using interactive code playgrounds that you can execute directly in your browser. You’ll have access to detailed explanations and visualizations for each problem to help you along the way.  
 
By the time you’re done, you’ll be able to use what you’ve learned to solve complex real-world problems and even advance more easily through your interviews at top tech companies.

Recursion for Coding Interviews in Java

The task is to reverse the string provided.

```Java
public static String reverseString(String myStr) {
  // Base case
  if (myStr.isEmpty()) {
    return myStr;
  }

  // Recursive case
  else {
    return reverseString(myStr.substring(1)) + myStr.charAt(0);
  }
}
```
What should the base case of the above mentioned code be?

The task is to reverse the string provided.
<pre><code class="language-Java">public static String reverseString(String myStr) {
 // Base case
 if (myStr.isEmpty()) {
 return myStr;
 }

 // Recursive case
 else {
 return reverseString(myStr.substring(1)) + myStr.charAt(0);
 }
}
</code></pre>
What should the base case of the above mentioned code be?

What is the output of the following code?
``` Java
public static int totalVowels(String text, int len, int index) {
  int count = 0;

  if (len == 0) {
    return 0;
  }
  char single = Character.toUpperCase(text.charAt(index));
  if (single == 'A' || single == 'E' || single == 'I' || single == 'O' || single == 'U') {
    count++;
  }
  return count + totalVowels(text, len-1, index+1);
}
public static void main(String args[])
{		
  	 String text = "thisisrecursion";
  	 int cnt = 0;
     cnt = recursiveFunc(text, text.length, 0);
     System.out.println(cnt);
}
```

What is the output of the following code?
<pre><code class="language-Java">public static int totalVowels(String text, int len, int index) {
 int count = 0;

 if (len == 0) {
 return 0;
 }
 char single = Character.toUpperCase(text.charAt(index));
 if (single == 'A' || single == 'E' || single == 'I' || single == 'O' || single == 'U') {
 count++;
 }
 return count + totalVowels(text, len-1, index+1);
}
public static void main(String args[])
{		
 	 String text = &quot;thisisrecursion&quot;;
 	 int cnt = 0;
 cnt = recursiveFunc(text, text.length, 0);
 System.out.println(cnt);
}
</code></pre>

This quiz will test your understanding of recursion with strings.

Fundamentals of Recursion

Iteration to Recursion

Recursion with Numbers

Recursion with Strings

Recursion with Arrays

Recursion with Data Structures

Quick Quiz on Recursion with Strings!