#include <stdio.h>

int islandPerimeter(int m, int n, int grid[m][n]){
    int perimeter = 0;
    // If only one island return 4
    if (m == 1 && n == 1){
        return 4;
    }
    // If one horizontal island
    if (m == 1){
        for (int j = 0; j < n; j++){
	    if (grid[0][j] == 1){
	        if (j == 0){
		    perimeter += 4 - grid[0][1];
	        }
	        else if (j == n - 1){
		    perimeter += 4 - grid[0][n - 2];
	        }
	        else{
		    perimeter += 4 - grid[0][j - 1] - grid[0][j + 1];
	        }
	    }
	}
	return perimeter;
    }
    // If one vertical island
    if (n == 1){
        for (int j = 0; j < m; j++){
	    if (grid[j][0] == 1){
	        if (j == 0){
		    perimeter += 4 - grid[1][0];
	        }
	        else if (j == m - 1){
		    perimeter += 4 - grid[m - 2][0];
	        }
	        else{
		    perimeter += 4 - grid[j - 1][0] - grid[j + 1][0];
	        }
	    }
	}
	return perimeter;
    }
    // All the other cases
    for (int i = 0; i < m; i++){
        for (int j = 0; j < n; j++){
            if (grid[i][j] == 1){
                if (i == 0){
                    if (j == 0){
                        perimeter += 4 - grid[i + 1][j] - grid[i][j + 1];
		    }
		    else if (j == n - 1){
			perimeter += 4 - grid[i + 1][j] - grid[i][j - 1];
		    }
		    else{
			perimeter += 4 - grid[i + 1][j] - grid[i][j - 1] - grid[i][j + 1];
		    }
		}
		else if (i == m - 1){
                    if (j == 0){
			perimeter += 4 - grid[i - 1][j] - grid[i][j + 1];
		    }
		    else if (j == n - 1){
			perimeter += 4 - grid[i - 1][j] - grid[i][j - 1];
		    }
		    else{
			perimeter += 4 - grid[i - 1][j] - grid[i][j - 1] - grid[i][j + 1];

		    }
		}
		else{
		    perimeter += 4 - grid[i + 1][j] - grid[i - 1][j] - grid[i][j - 1] - grid[i][j + 1];
		}	
	    }
	}
    }
    return perimeter;
}