924spiral.c

#include <stdio.h>
#define maxRow 15 //最大行数
int main(){
  int n,y,x;          //正方行列の大きさ。
  int count  = 0; //文字を入れ終わった回数。
  char arr[maxRow][maxRow];   //行列。
  char printChar = 'Z';       //初期位置の文字。ここをYやCにしても動くように対応。
  enum directions { UP,LEFT,DOWN,RIGHT };
  enum directions direction = UP;
  printf("n = ");  
  while(scanf("%d", &n) != 1 || n < 3 || n > maxRow) {
    printf("#matrix must be at least 3 and at most %d.\n",maxRow);
    while(getchar() != '\n') {}; 
    printf("n = ");
  }
  for(y=0;y<n;y++) {
    for(x=0;x<n;x++) {
      arr[y][x] = '$';
    }
  }
  x = n/2;
  y = n/2;
  while(count != n*n) {
    arr[y][x] = 'Z'-(('Z'-printChar+count)%26);
    count++;
    switch(direction) {
      case UP:
        y--;
        if(arr[y][x-1] == '$') direction = LEFT;
        break;

      case LEFT:
        x--;
        if(arr[y+1][x] == '$') direction = DOWN;        
        break;

      case DOWN:
        y++;
        if(arr[y][x+1] == '$') direction = RIGHT;
        break;

      case RIGHT:
        x++;
        if(arr[y-1][x] == '$') direction = UP;
        break;
    }
  }
  for(y=0;y<n;y++) {
    for(x=0;x<n;x++) {
      printf("%c ",arr[y][x]);
    }
    puts("");
  }
  return 0;
}