Grokking Data Structures & Algorithms for Coding Interviews

Solution: Search a 2D Matrix II

## Problem Statement
Given a 2D grid of size `m x n` `matrix` containing integers, and integer `target`, return `true` if `target` value exists in the `matrix`. Otherwise, return false.

The `matrix` has the following properties:
- Values in each column are sorted in `non-decreasing order` from `top to bottom`.
- Values in each row are sorted in `non-decreasing order` from `left to right`.


### Examples

**Example 1:**
  - **Input:** target = 5, matrix = 
```
[[1,2,3],
 [4,5,6],
 [7,8,9]]
```
  - **Expected Output:** `true`