Coast length, kattis - c

Question

I'm trying to solve one problem, which I found on website https://open.kattis.com/problems/coast. Tl;dr version of problem is, that for given map of landscape, I should print out length of coastline (without inner islands).
I receive 0/26 mark, but I have no idea why, I've tested, and as far as i checked, it worked. I assume it doesn't compile, but if that is the case, why is that? It compiles for me perfectly fine.
#include <stdio.h>
int edgeCount(int, int, char*);
int topToBottomCount(int, int, char*);
int leftToRightCount(int, int, char*);
int removingInsides(int, int, char*);
int main()
{
int n = 0; // number of strings
int m = 0; // strings lenghts
//printf("Enter N(number of strings) x M(strings lenght): ");
scanf("%d", &n);
scanf("%d", &m);
char coast[1024];
for(int i = 0; i < n; i++){
scanf("%s", coast+i*m); // adding strings to char coast[1024], making array of ones and zeroes // e.g we are adding 3x4 strings - 111100001111
} // it can also be looked as 1111
// 0000 - matrix
int coasts = edgeCount(n, m, coast); // 1111
coasts += topToBottomCount(n, m, coast);
coasts += leftToRightCount(n, m, coast);
coasts -= removingInsides(n, m, coast);
printf("%d - coasts\n", coasts);
return 0;
}
int edgeCount(int n, int m, char *coast){ // if 1 is placed at the edge of the "map", it is 1 coast (2 if it is at corner)
int edgeCoast = 0;
for(int i = 0; i < m; i++){ // top edges
if(coast[i] == '1')
edgeCoast++;
}
for(int i = m*n - m; i < m*n; i++){ // bottom edges (m*n - m = first char in the last string, it can be also looked as the last row in matrix)
if(coast[i] == '1')
edgeCoast++;
}
for(int i = 0; i <m*n; i+=m){ // left side edges (first column in matrix)
if(coast[i] == '1')
edgeCoast++;
}
for(int i = m-1; i < m*n; i+=m){ // right side edges (last column in matrix)
if(coast[i] == '1')
edgeCoast++;
}
return edgeCoast;
}
int topToBottomCount(int n, int m, char *coast){
int coasts = 0;
for(int i = 0; i < m*n - m; i++){ // we start from first char in "matrix", and move to the (m*n - m = 2nd last "row")
if(coast[i] ^ coast[i+m]) // we are checking if zero is placed above one or via versa
coasts++;
}
return coasts;
}
int leftToRightCount(int n, int m, char* coast){
int coasts = 0;
int p = m-1;
for(int i = 0; i < n*m; i++){ // we start from the first charr, and we are going trough whole matrix, but the last column
if(i == p){ // p = m - 1 (last char in first row)
p+=m; // p+=m (last char in next column, and so on)
continue; // we move to next iteration
}
if(i == m*n - 1) //if we are at last char in matrix, we break out from loop
break;
if(coast[i] ^ coast[i+1])
coasts++;
}
return coasts;
}
int removingInsides(int n, int m, char* coast){ // Lakes and islands in lakes are not contributing to the sea coast. we are checking if they exist.
int innerCoasts = 0;
for(int i = m + 1; i < n*m - m - 1; i ++){
if( coast[i] == '0' && coast[i] ^ coast[i-1] && coast[i] ^ coast[i+1] && coast[i] ^ coast[i-m] && coast[i] ^ coast[i+m]) // char has to be 0, and to hist left, right, above and under there has to be 1
innerCoasts++;
}
return innerCoasts * 4; // *4 because we added 4 coasts before for each island.
}

Answer 1

I tried compiling your code using the GCC C++ compiler (4.9.2). It compiled fine and I tested it using the sample problem in the link you provided. It spit out the right answer.
However, when I tried compiling using the GCC C compiler (also v 4.9.2), it fails with 'for' loop initial declarations are only allowed in C99 or C11 mode, which is explained by this SO question. I think your assignment was graded using a C compiler and the compilation of your program failed due to this error.