UVA 639_Don't_Get_Rooked

#include <stdio.h>
#include <stdlib.h>

#define MAX 4

int max(int value1, int value2){
    if (value1>value2) return value1;
    return value2;
}

void reset_board(int board[MAX][MAX]){
    int i,j;
    for (i=0;i<MAX;i++)
        for (j=0;j<MAX;j++)
            board[i][j] = 0;
}

void fill_board(int board[MAX][MAX], int board_size){
    int i=0, j;
    char c;
    while (i<board_size){
        j= 0;
        while (j<board_size){
            c= getchar();
            if (c == '\n')
                continue;
            if (c=='X')
                board[i][j] = -1;
            j++;
        }
        i++;
    }
}

void get_next(int x, int y, int board_size, int* next_x, int* next_y){
    *next_x = x+1;
    *next_y = y;
    if (*next_x == board_size){
        *next_x = 0;
        *next_y = y+1;
    }

}

int is_legal(int x, int y, int board[MAX][MAX], int board_size){
    if ((board[x][y] == -1) || (board[x][y] == 1))
        return 0;

    int i;
    for (i=x-1; i>=0 && board[i][y] != -1; i--){
        if (board[i][y] == 1)
            return 0;
    }

    int j;
    for (j=y-1;j>=0 && board[x][j] != -1; j--){
        if (board[x][j] == 1)
            return 0;
    }

    return 1;
}

void solve_DGR(int x, int y, int board[MAX][MAX], int board_size, int* current_max, int* overall_max){
    if (y==board_size){
        *overall_max = max(*current_max, *overall_max);
        return;
    }
    int next_x, next_y;
    get_next(x, y, board_size, &next_x, &next_y);
    if (is_legal(x, y, board, board_size)){
        board[x][y] = 1;
        (*current_max)++;
        solve_DGR(next_x, next_y, board, board_size, current_max, overall_max);
        board[x][y] = 0; /*BACKTRACK*/
        (*current_max)--;
    }
    solve_DGR(next_x, next_y, board, board_size, current_max, overall_max);

    return;
}

int main(int argc, char** argv) {
    int board_size;
    int board[MAX][MAX];
    int current_max;
    int overall_max;

    scanf("%d", &board_size);
    while (board_size >0){
        current_max = 0;
        overall_max = 0;
        reset_board(board);
        fill_board(board, board_size);
        solve_DGR(0,0, board, board_size, &current_max, &overall_max);
        printf("%d\n", overall_max);
        scanf("%d", &board_size);
    }

    return (EXIT_SUCCESS);
}