Google Code Jam 2013 Qualifying Round A

gcj-a.c

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

int cmp( char a, char b);
int check_corners( uint8_t cur, char board[4][4]);
int check_stripes( uint8_t cur, char board[4][4]);
int check_ongoing( uint8_t cur, char board[4][4]);

int main( int argc, char **argv ) {
  FILE *file = fopen( argv[1], "r" );
  if ( !file ) {
    printf("Unable to open file: %s\n", argv[1]);
    return 1;
  }

  int boards;
  fscanf(file, "%1d", &boards);
  uint8_t a, b, current, result;

  for ( current = 1; current <= boards; current++ ) {
    char board[4][4];

    for ( uint8_t i = 0; i < 4; i++ ) {
      fread(board[i], 1, 4, file); // read entire line at once, it's aligned anyway
      fseek(file, 1, SEEK_CUR); // newline between rows
    }
    fseek(file, 1, SEEK_CUR); // newline between boards

    do {
      // check if corners match
      if (! check_corners(current, board) ) {
        result = 1;
      }
      // check if stripes match
      else if (! check_stripes(current, board) ) {
        result = 1;
      }
      // check if game isn't over yet
      else if (! check_ongoing(current, board) ) {
        result = 1;
      }
      // oh snap it's a draw
      else {
        printf("Case #%d: Draw\n", current);
        result = 1;
      }
    } while (result == 0);

  }

  fclose(file);
  return 0;
}

int cmp( char a, char b ) {
  if ( strcmp(&a, ".") || strcmp(&b, ".") )
    return 1;

  if ( strcmp(&a, &b) || strcmp(&a, "T") || strcmp(&b, "T") )
    return 0;

  return 1;
}

int check_corners( uint8_t cur, char board[4][4] ) {
  // start from top left
  char s = board[0][0];

  // compare to top right
  if ( cmp(s, board[0][3]) ) {
    if ( cmp(s, board[0][1]) && cmp(s, board[0][2]) ) {

      if (! strcmp(&s, "T") ) {
        printf("Case #%d: %s won\n", cur, &board[0][3]);
      } else {
        printf("Case #%d: %s won\n", cur, &s);
      }

      return 0;
    }
  }

  // compare to bottom left
  else if ( cmp(s, board[3][0]) ) {
    if ( cmp(s, board[1][0]) && cmp(s, board[2][0]) ) {

      if (! strcmp(&s, "T") ) {
        printf("Case #%d: %s won\n", cur, &board[3][0]);
      } else {
        printf("Case #%d: %s won\n", cur, &s);
      }

      return 0;
    }
  }

  // compare to bottom right
  else if ( cmp(s, board[3][3]) ) {
    if ( cmp(s, board[1][1]) && cmp(s, board[2][2]) ) {

      if (! strcmp(&s, "T") ) {
        printf("Case #%d: %s won\n", cur, &board[2][3]);
      } else {
        printf("Case #%d: %s won\n", cur, &s);
      }

      return 0;
    }
  } else {

    // switch to top right
    s = board[0][3];

    // compare to bottom left
    if ( cmp(s, board[3][0]) ) {
      if ( cmp(s, board[1][2]) && cmp(s, board[2][1]) ) {

        if (! strcmp(&s, "T") ) {
          printf("Case #%d: %s won\n", cur, &board[2][3]);
        } else {
          printf("Case #%d: %s won\n", cur, &s);
        }

        return 0;
      }
    }

    // compare to bottom right
    else if ( cmp(s, board[3][3]) ) {
      if ( cmp(s, board[1][3]) && cmp(s, board[2][3]) ) {

        if (! strcmp(&s, "T") ) {
          printf("Case #%d: %s won\n", cur, &board[2][3]);
        } else {
          printf("Case #%d: %s won\n", cur, &s);
        }

        return 0;
      }
    }
    else {

      // switch to bottom left
      s = board[3][0];

      // compare to bottom right
      if ( cmp(s, board[3][3]) ) {
        if ( cmp(s, board[3][1]) && cmp(s, board[3][2]) ) {

          if (! strcmp(&s, "T") ) {
            printf("Case #%d: %s won\n", cur, &board[3][3]);
          } else {
            printf("Case #%d: %s won\n", cur, &s);
          }

          return 0;
        }
      }
    }
  }

  // no matching corners
  return 1;
}

int check_stripes( uint8_t cur, char board[4][4] ) {
  char s = board[0][1];

  if ( cmp(s, board[3][1]) ) {
    if ( cmp(s, board[1][1]) && cmp(s, board[2][1]) ) {

      if (! strcmp(&s, "T") ) {
        printf("Case #%d: %s won\n", cur, &board[3][1]);
      } else {
        printf("Case #%d: %s won\n", cur, &s);
      }

      return 0;
    }
  } else {
    s = board[0][2];

    if ( cmp(s, board[3][2]) ) {
      if ( cmp(s, board[1][2]) && cmp(s, board[2][2]) ) {

        if (! strcmp(&s, "T") ) {
          printf("Case #%d: %s won\n", cur, &board[3][2]);
        } else {
          printf("Case #%d: %s won\n", cur, &s);
        }

      return 0;
      }

    } else {
      s = board[1][0];

      if ( cmp(s, board[1][3]) ) {
        if ( cmp(s, board[1][1]) && cmp(s, board[1][2]) ) {

          if (! strcmp(&s, "T") ) {
            printf("Case #%d: %s won\n", cur, &board[1][0]);
          } else {
            printf("Case #%d: %s won\n", cur, &s);
          }

        return 0;
        }
      } else {
        s = board[2][0];

        if ( cmp(s, board[2][3]) ) {
          if ( cmp(s, board[2][1]) && cmp(s, board[2][2]) ) {

            if (! strcmp(&s, "T") ) {
              printf("Case #%d: %s won\n", cur, &board[2][0]);
            } else {
              printf("Case #%d: %s won\n", cur, &s);
            }

          return 0;
          }
        }
      }
    }
  }

  // no matching strips
  return 1;
}

int check_ongoing( uint8_t cur, char board[4][4] ) {
  for ( uint8_t i = 0; i < 16; i++ ) {
    if ( strcmp(board[i], ".") ) {
      printf("Case #%d: Game has not completed\n", cur);
      return 0;
    }
  }
  return 1;
}