Commit e9ea25d

1. Find the first land.

* There are two major ways to explore a `connected components` (island): **Breadth-First Search** and **Depth-First Search**.

* For **Depth-First Search**, there are two ways to make it: `Recursive` and `Iterative`. So I will provide 3 solutions in total.

* Mark each found land as `V` which represents `visited`. Visited lands don't need to be visited again.

1. After all lands on an island have been visited, look for the next non-visited land.

Please click [Depth-First Search by Recursion Solution](0200-number-of-islands.md) for `200. Number of Islands` to view.

In solution 1, we have known how to traverse a graph by recursion. Computer language support for recursive calls is implemented through stacks.

For every recursive solution, there is an iterative solution, which means the same problem can be solved using loops.

The benefit of using iteration is better program performance. After all, recursive calls are expensive.

1. Find the first land.

* There are two major ways to explore a `connected components` (island): **Breadth-First Search** and **Depth-First Search**.

* For **Depth-First Search**, there are two ways to make it: `Recursive` and `Iterative`. So I will provide 3 solutions in total.

* Mark each found land as `V` which represents `visited`. Visited lands don't need to be visited again.

1. After all lands on an island have been visited, look for the next non-visited land.

From this sample code bellow, you can see that starting from a node, through recursive calls, it goes up until it can't go any further, turns right, and continues up. The priority order of directions is `up, right, down, and left`.

adjacent_points = [