```
/*
* Author: Arpit Bhayani
* https://arpitbhayani.me
*/
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <climits>
#include <deque>
#include <iostream>
#include <list>
#include <limits>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <vector>
#define ll long long
#define MIN(a, b) a < b ? a : b
#define MAX(a, b) a > b ? a : b
using namespace std;
int readline(char *str) {
int i = 0;
char ch;
while((ch = getchar()) != '\n') {
str[i++] = ch;
}
str[i] = '\0';
return i;
}
int safe(int i, int j, int row, int col) {
if(i >= 0 && j >= 0 && i < row && j < col) {
return 1;
}
return 0;
}
void dfs(char **grid, int i, int j, int row, int col, int ** visited) {
if(visited[i][j] == 1) {
return;
}
int arrx[4] = {1, -1, 0, 0};
int arry[4] = {0, 0, 1, -1};
visited[i][j] = 1;
for(int l = 0; l < 4; l++) {
int ni = i + arrx[l];
int nj = j + arry[l];
if(safe(ni, nj, row, col) && grid[ni][nj] == '1') {
dfs(grid, ni, nj, row, col, visited);
}
}
}
int numIslands(char** grid, int gridRowSize, int gridColSize) {
int row = gridRowSize, col = gridColSize;
int ** visited = (int **) calloc(row, sizeof(int *));
for(int i = 0 ; i < row ; i++) {
visited[i] = (int *) calloc(col, sizeof(int));
}
int count = 0;
for(int i = 0 ; i < row; i++) {
for(int j = 0 ; j < col; j++) {
if(visited[i][j] == 0 && grid[i][j] == '1') {
dfs(grid, i, j, row, col, visited);
count++;
}
}
}
for(int i = 0 ; i < row ; i++) {
free(visited[i]);
}
free(visited);
return count;
}
int main(int argc, char *argv[]) {
int row, col;
scanf("%d%d", &row, &col);
char **grid = (char **) malloc(row * sizeof(char *));
for(int i = 0 ; i < row ; i++) {
grid[i] = (char *) malloc((col + 1) * sizeof(char));
}
for(int i = 0 ; i < row ; i++) {
scanf("%s", grid[i]);
}
printf("%d\n", numIslands(grid, row, col));
return 0;
}
```

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