Grokking the Coding Interview: Patterns for Coding Questions

Solution: Decimal to Binary Conversion 

## Problem Statement

Given a positive integer `n`, write a function that returns its binary equivalent as a string. The function should not use any in-built binary conversion function.

### Examples

**Example 1:**
```
Input: 2
Output: "10"
Explanation: The binary equivalent of 2 is 10.
```

**Example 2:**
```
Input: 7
Output: "111"
Explanation: The binary equivalent of 7 is 111.
```

**Example 3:**
```
Input: 18
Output: "10010"
Explanation: The binary equivalent of 18 is 10010.
```

**Constraints:**

- 0 <= num <= 10<sup>9</sup>

## Solution


We can use a stack to efficiently create the binar