Place 8 Queens on Chessboard

CMakeLists.txt

project(eight_queens)
cmake_minimum_required(VERSION 2.8)
aux_source_directory(. SRC_LIST)
add_executable(${PROJECT_NAME} ${SRC_LIST})

main.c

#include <stdio.h>
#include <assert.h>

#define ROWS 8
#define COLS ROWS

typedef int field_t[ROWS][COLS];

void print_field(field_t *f)
{
  for (int r = 0; r < 8; r++)
  {
    for (int c = 0; c < 8; c++)
    {
      printf(" %c ", ((*f)[r][c] ? '*': '.'));
    }
    printf("\n");
  }
}

int is_position_under_attack(field_t *f, int r, int c)
{
  int dc[8] = {-1, -1,  0, 1, 1,  1,  0, -1};
  int dr[8] = { 0,  1,  1, 1, 0, -1, -1, -1};

  for (int d = 0; d < 8; d++)
  {
    int max_len = (ROWS > COLS ? ROWS : COLS);
    for (int l = 1; l < max_len; ++l)
    {
      int nr = r + l * dr[d];
      int nc = c + l * dc[d];

      if (nr < 0 || nr >= ROWS || nc < 0 || nc >= COLS)
        continue;

      if ((*f)[nr][nc])
        return 1;
    }
  }

  return 0;
}

int place_queens(field_t *f, int r)
{
  if (r >= ROWS)
  {
    // All queens placed. Return success.
    return 1;
  }

  for (int c = 0; c < COLS; ++c)
  {
    if (!is_position_under_attack(f, r, c))
    {
      (*f)[r][c] = 1;
      if (place_queens(f, r + 1))
      {
        // Successfully placed all remaining queens.
        return 1;
      }
      (*f)[r][c] = 0;
    }
  }

  // No such placement.

  //printf("falling back!\n");
  //print_field(f);

  return 0;
}

int main()
{
  field_t f = {0};

  int result = place_queens(&f, 0);
  if (result)
  {
    print_field(&f);
  }
  else
  {
    printf("No such placement.\n");
  }

  return 0;
}