If you’ve ever struggled with solving problems using recursion, or if you have to brush up your skills for an interview, this course is for you.

We'll start with the basics of what recursion is and why it’s important before diving into practicing solving actual questions. You’ll have access to detailed explanations and visualizations for each problem to help you along the way. 

By the time you have completed this course, you’ll be able to use all the concepts to solve complex real-world problems. We hope that through practicing recursion, you will be able to ace all recursion related questions in interviews at top tech companies.

Solving Problems with Recursion in Python

def decimalToBinary(testVariable) :
  # Base Case
  if testVariable <= 1:
    return str(testVariable)

  # Recursive Case
  else:
    return decimalToBinary(testVariable // 2) + decimalToBinary(testVariable % 2) # Floor division - 
      # division that results into whole number adjusted to the left in the number line

# Driver Code
testVariable = 11
print(decimalToBinary(testVariable))

### Explanation:

The simple method for converting a decimal number to a binary number is to keep track of the $remainder$ and the leftover $dividend$ when a number is divided by $2$.
Look at the illustration below:

We continue dividing the number by $2$ until we are left with $1$.

Since $1$ divided by $2$ gives $remainder$ $1$; this will be our **base case**:
```
if testVariable <= 1:
    return str(testVariable)
```

In the recursive case:
```python
return decimalToBinary(testVariable // 2) + decimalToBinary(testVariable % 2)
```
we keep track of the remaining $dividend$ and the $remainder$ respectively. Have a look at the sequence of function calls to have an idea of how recursion occurs in this case.

---
In the next lesson, we have a short quiz for you to test your concepts.

## Explanation:

The simple method for converting a decimal number to a binary number is to keep track of the $remainder$ and the leftover $dividend$ when a number is divided by $2$.
Look at the illustration below:

Solution Review: Convert Decimal Number to Binary Number

Solution: Using Recursion

Explanation: