<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 rows;
    int cols;
    vector<pair<int,int>> directions = {{-1,0}, {1,0}, {0,-1}, {0,1}};

    bool valid( int row, int col ){
        return row >= 0 && row < rows && col >= 0 && col < cols;
    }

    int countSides( int row, int col, vector<vector<int>>& grid){
        int count = 4;
        
        for( auto& dir : directions ){
            
            int newRow = row + dir.first;
            int newCol = col + dir.second;

            if( valid(newRow, newCol) && grid[newRow][newCol] == 1 ){
                count--;
            }
        }

        return count;

    }

    int islandPerimeter(vector<vector<int>>& grid) {

        rows = grid.size();

        if( rows == 0){
            return 4;
        }

        cols = grid[0].size();

        queue<pair<int,int>> qu;
        set<pair<int,int>> seen;
        int out = 0;

        int row, col;
        bool found = false;
        for( row = 0; row < rows; ++row){
            for( col = 0; col < cols; ++col ){
                if( valid(row,col) && grid[row][col] == 1){
                    found = true;
                    break;
                }
            }
            if( found ){
                break;
            }
        }

        if( !found ){
            return 0;
        }

        qu.push({row,col});
        seen.insert({row,col});
 
        while( !qu.empty() ){

            auto [row, col] = qu.front();
            qu.pop();

            out += countSides( row, col, grid );

            for( auto& dir : directions ){
                
                int newRow = row + dir.first;
                int newCol = col + dir.second;

                if( valid(newRow, newCol) && seen.find({newRow, newCol}) == seen.end() && grid[newRow][newCol] == 1){
                    seen.insert({newRow,newCol});
                    qu.push( {newRow, newCol});
                }

            }


        }


        return out;
    }
};
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