<p>You are given <code>row x col</code> <code>grid</code> representing a map where <code>grid[i][j] = 1</code> represents&nbsp;land and <code>grid[i][j] = 0</code> represents water.</p>

<p>Grid cells are connected <strong>horizontally/vertically</strong> (not diagonally). The <code>grid</code> is completely surrounded by water, and there is exactly one island (i.e., one or more connected land cells).</p>

<p>The island doesn&#39;t have &quot;lakes&quot;, meaning the water inside isn&#39;t connected to the water around the island. One cell is a square with side length 1. The grid is rectangular, width and height don&#39;t exceed 100. Determine the perimeter of the island.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img src="https://assets.leetcode.com/uploads/2018/10/12/island.png" style="width: 221px; height: 213px;" />
<pre>
<strong>Input:</strong> grid = [[0,1,0,0],[1,1,1,0],[0,1,0,0],[1,1,0,0]]
<strong>Output:</strong> 16
<strong>Explanation:</strong> The perimeter is the 16 yellow stripes in the image above.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> grid = [[1]]
<strong>Output:</strong> 4
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> grid = [[1,0]]
<strong>Output:</strong> 4
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>row == grid.length</code></li>
	<li><code>col == grid[i].length</code></li>
	<li><code>1 &lt;= row, col &lt;= 100</code></li>
	<li><code>grid[i][j]</code> is <code>0</code> or <code>1</code>.</li>
	<li>There is exactly one island in <code>grid</code>.</li>
</ul>

class Solution {
public:
    int islandPerimeter(vector<vector<int>>& grid) {
        // find the land by iterating across the grid until finding a 1
        // Add the first piece of land on to a queue
        // Track the visited nodes by turning visited nodes to 2


        // Find the land
        pair<int, int> initial_land;
        bool found_land = false;
        for (int i = 0; i < grid.size() && !found_land; i++) {
            for (int j = 0; j < grid[i].size(); j++) {
                if (grid[i][j] == 1) {
                    initial_land.first = i;
                    initial_land.second = j;
                    found_land = true;
                    break;
                }
            }
        }

        queue<pair<int, int>> discovered;
        discovered.push(initial_land);
        int perimeter = 0;

        while (!discovered.empty()) {
            pair<int, int> land = discovered.front();
            discovered.pop();
            if (grid[land.first][land.second] == 2){
                continue;
            }

            // Check land's border for neighoring land cells and water that can be added to the perimeter

            // row - 1
            if (land.first - 1 < 0 || grid[land.first - 1][land.second] == 0) {
                // if edge or water
                perimeter++;
            } else if (grid[land.first - 1][land.second] == 1) {
                // if land
                discovered.push(pair<int, int>(land.first - 1, land.second));
            }
            // row + 1
            if (land.first + 1 >= grid.size() || grid[land.first + 1][land.second] == 0) {
                // if edge or water
                perimeter++;
            } else if (grid[land.first + 1][land.second] == 1) {
                // if land
                discovered.push(pair<int, int>(land.first + 1, land.second));
            }
            // col - 1
            if (land.second - 1 < 0 || grid[land.first][land.second - 1] == 0) {
                // if edge or water
                perimeter++;
            } else if (grid[land.first][land.second - 1] == 1) {
                // if land
                discovered.push(pair<int, int>(land.first, land.second - 1));
            }
            // col + 1
            if (land.second + 1 >= grid[land.first].size() || grid[land.first][land.second + 1] == 0) {
                // if edge or water
                perimeter++;
            } else if (grid[land.first][land.second + 1] == 1) {
                // if land
                discovered.push(pair<int, int>(land.first, land.second + 1));
            }


            // Mark as visited
            grid[land.first][land.second] = 2;
        }

        return perimeter;
    }
};
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