Learn essential coding patterns to answer problems and prepare for tech companies' interviews.

Ace the JavaScript Coding Interview

This module teaches us the underlying patterns behind common coding interview questions. By learning these essential patterns, we'll be able to unpack and answer any problem the right way—just by assessing the problem statement. This approach was created by FAANG hiring managers to help us prepare for the typical rounds of interviews at major tech companies like Apple, Google, Meta, Microsoft, and Amazon.

By the end of this module, we'll have the skills we need to unlock even the most challenging questions, grok the coding interview, and level up our career with confidence.

Coding Interview Patterns

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## Statement

Imagine an island with a rectangular shape that touches both the Pacific and Atlantic oceans. The northern and western sides meet the Pacific, while the southern and eastern sides touch the Atlantic. This island is divided into square cells.

To depict the height above sea level of each cell, we use an integer matrix, `heights`, of size $(m \times n)$. Here, `heights[r][c]` represents the elevation of the cell at coordinate $(r, c)$.

When heavy rain pours down on the island every few months, water flows from the island to both the Pacific and Atlantic oceans. The path of flow depends on the heights of the cells. 

Consider a cell with a height of $9$ that's higher than or equal to its neighboring cells to the north, east, west, and south. This indicates that water can flow from this cell to adjacent ones. Similarly, this process is repeated until the flow of water either reaches the Pacific or Atlantic border or a cell that can not flow water to any of its neighbors.  If the flow of water starting from a cell can direct water to both the Pacific and Atlantic Ocean borders, we include it in the output.

> **Note:** Any cell adjacent to an ocean can channel water into the ocean.

With this information, your task is to return a 2D array of coordinates. Each entry $(r_i, c_i)$ in this array indicates that rainwater can flow from the cell at coordinate $(r_i, c_i)$ to both the Pacific and Atlantic oceans.

**Constraints:**

* $m ==$ `heights.length`

* $n ==$ `heights[r].length`, where $0 \leq r \lt m$

* $1 \leq m$, $n \leq 30$

* $0 \leq$ `heights[r][c]` $\leq 10^3$

## Examples

Try to solve the Pacific Atlantic Water Flow problem.