<p>Given a 2D&nbsp;<code>grid</code> consists of <code>0s</code> (land)&nbsp;and <code>1s</code> (water).&nbsp; An <em>island</em> is a maximal 4-directionally connected group of <code><font face="monospace">0</font>s</code> and a <em>closed island</em>&nbsp;is an island <strong>totally</strong>&nbsp;(all left, top, right, bottom) surrounded by <code>1s.</code></p>

<p>Return the number of <em>closed islands</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<p><img alt="" src="https://assets.leetcode.com/uploads/2019/10/31/sample_3_1610.png" style="width: 240px; height: 120px;" /></p>

<pre>
<strong>Input:</strong> grid = [[1,1,1,1,1,1,1,0],[1,0,0,0,0,1,1,0],[1,0,1,0,1,1,1,0],[1,0,0,0,0,1,0,1],[1,1,1,1,1,1,1,0]]
<strong>Output:</strong> 2
<strong>Explanation:</strong> 
Islands in gray are closed because they are completely surrounded by water (group of 1s).</pre>

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

<p><img alt="" src="https://assets.leetcode.com/uploads/2019/10/31/sample_4_1610.png" style="width: 160px; height: 80px;" /></p>

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

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

<pre>
<strong>Input:</strong> grid = [[1,1,1,1,1,1,1],
&nbsp;              [1,0,0,0,0,0,1],
&nbsp;              [1,0,1,1,1,0,1],
&nbsp;              [1,0,1,0,1,0,1],
&nbsp;              [1,0,1,1,1,0,1],
&nbsp;              [1,0,0,0,0,0,1],
               [1,1,1,1,1,1,1]]
<strong>Output:</strong> 2
</pre>

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

<ul>
	<li><code>1 &lt;= grid.length, grid[0].length &lt;= 100</code></li>
	<li><code>0 &lt;= grid[i][j] &lt;=1</code></li>
</ul>

class Solution {
public:
    int n, m;
    vector<pair<int, int>> d = {{0, 1}, {0, -1}, {-1, 0}, {1, 0}};
    bool flag;
    bool vis[105][105];
    bool valid(int si, int sj) {
        if (si >= 0 && si < n && sj >= 0 && sj < m)
            return true;
        return false;
    };
    void bfs(int si, int sj, vector<vector<int>>& grid) {
       
        queue<pair<int,int>> pq;
        pq.push({si,sj});
        vis[si][sj] = true;
         while(!pq.empty()){
            auto [cur_i, cur_j] = pq.front();
            pq.pop();
              if (cur_i == 0 || cur_i == n - 1 || cur_j == 0 || cur_j == m - 1)
            flag = false;
            for (int i = 0; i < 4; i++) {
            int ci = cur_i + d[i].first;
            int cj = cur_j + d[i].second;
            if (valid(ci, cj) && !vis[ci][cj] && grid[ci][cj] == 0) {
                vis[ci][cj] = true;
                pq.push({ci,cj});

            }
        }
         }
        
    }


    int closedIsland(vector<vector<int>>& grid) {
        memset(vis, false, sizeof(vis));
        n = grid.size();
        m = grid[0].size();
        int ans = 0;
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < m; j++) {
                if (!vis[i][j] && grid[i][j] == 0) {
                    flag = true;
                    bfs(i, j, grid);
                    if (flag)
                        ans++;
                }
            };
        }
        return ans;
    }
};
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