<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:
    vector<vector<int>> v;
    vector<pair<int, int>> chk = {{-1, 0}, {1, 0}, {0, -1}, {0, 1}};
    bool vis[500][500];
    int per = 0;
    int row, col;

    int islandPerimeter(vector<vector<int>>& grid) {
        v = grid;
        memset(vis, false, sizeof(vis));
        row = v.size();
        col = v[0].size();
        for(int i=0; i<v.size(); i++) {
            for(int j=0; j<v[i].size(); j++) {
                if(grid[i][j] == 1) {
                    valid_cnt(i, j);
                }
            }
        }

        return per;
    }

    void valid_cnt(int src_i, int src_j) {

        for(auto it : chk) {
            int c_i = src_i + it.first;
            int c_j = src_j + it.second;

            if(c_i < 0 || c_j < 0 || c_i >= row || c_j >= col) {
                per++;
            } else {
                if(v[c_i][c_j] != 1) {
                    per++;
                } 
            }
        }
    }
};
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