Grokking Dynamic Programming Patterns for Coding Interviews

Solution: Staircase

## Problem Statement
Given a stair with 'n' steps, implement a method to count how many possible ways are there to reach the top of the staircase, given that, at every step you can either take 1 step, 2 steps, or 3 steps.

**Example 1:**
```
Number of stairs (n) : 3
Number of ways = 4
Explanation: Following are the four ways we can climb : {1,1,1}, {1,2}, {2,1}, {3} 
```

**Example 2:**
```
Number of stairs (n) : 4
Number of ways = 7
Explanation: Following are the seven ways we can climb : {1,1,1,1}, {1,1,2}, {1,2,1}, {2,1,1}, 
{2,2}, {1,3}, {3,1}
```

**Constraints:**

- `1 <= n <= 45`