<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:
    def islandPerimeter(self, grid: List[List[int]]) -> int:
        row,col = len(grid),len(grid[0])
        per = [0]
        si,sj =0,0
        flag = False
        vis = {}
        for i in range(len(grid)):
            for j in range(len(grid[0])):
                if grid[i][j] == 1:
                    flag = True
                    si,sj =i,j
                    break
            if flag:
                break
        
        moves = [(0,1),(1,0),(0,-1),(-1,0)]

        def perimeter(r,c):
            if r<0 or r>=row or c<0 or c >=col or grid[r][c] == 0 or vis.get((r,c),0) == 1:
                return
            
            per[0]+=4
            vis[(r,c)] = 1
            for mov in moves:
                ri,cj = r+mov[0] ,c+mov[1]
                if 0<=ri<row and 0<=cj<col and grid[ri][cj] == 1:
                    perimeter(ri,cj)
                    per[0]-=1
                    
        perimeter(si,sj)

        return per[0]

        
       
23303