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Unique Paths
Difficulty: Medium
Category: DSA
Topics: Math, Dynamic Programming, Combinatorics
Asked at: Amazon, Bloomberg, ByteDance, Facebook, Goldman Sachs, Google, Microsoft, Qualtrics, Salesforce, VMware
There is a robot on an `m x n` grid. The robot is initially located at the **top-left corner** (i.e., `grid[0][0]`). The robot tries to move to the **bottom-right corner** (i.e., `grid[m - 1][n - 1]`). The robot can only move either down or right at any point in time.
Given the two integers `m` and `n`, return _the number of possible unique paths that the robot can take to reach the bottom-right corner_.
The test cases are generated so that the answer will be less than or equal to `2 * 109`.
**Example 1:**
**Input:** m = 3, n = 7
**Output:** 28
```
**Example 2:**
**Input:** m = 3, n = 2
**Output:** 3
**Explanation:** From the top-left corner, there are a total of 3 ways to reach the bottom-right corner:
1. Right -> Down -> Down
2. Down -> Down -> Right
3. Down -> Right -> Down
```
**Constraints:**
- `1 <= m, n <= 100`
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