Island.cpp

#include<bits/stdc++.h>
using namespace std;

 int numIslands(vector<vector<char>>& grid) {
        int m = grid.size(), n = m ? grid[0].size() : 0;
        int count = 0;
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                if (grid[i][j] == '1') {
                    dfs(grid, i, j);
                    count++;
                }
            }
        }
        return count;
 }


void dfs(vector<vector<char>>& grid, int i, int j) {
        int m = grid.size(), n = grid[0].size();
        if (i < 0 || i == m || j < 0 || j == n || grid[i][j] == '0') {
            return;
        }
        grid[i][j] = '0';
        dfs(grid, i - 1, j);
        dfs(grid, i + 1, j);
        dfs(grid, i, j - 1);
        dfs(grid, i, j + 1);
}


int main(){


    int n,m; cin>>n>>m;


    vector<vector<char>> grid(n,vector<char>(m));


    for(int i=0;i<n;i++){
        for(int j=0;j<m;j++){
            cin>>grid[i][j];
        }
    }

    cout<<numIslands(grid);

    return 0;
}