Fraction

#include <stdio.h>
#include <stdlib.h>
#define DIGITMAX 101 /* 100 + dummy */
void recurringDecimal(int x, int y) {
  int rem[DIGITMAX], quo[DIGITMAX],  r = 0, i, remainder, loop = 0;
  rem[r] = 0; quo[r++] = 0; /* dummy */
  printf("%d.", x / y);
  while (x != 0) {
    remainder = x % y;
    if (!remainder) break;
    for (i = 1; i < r; i++)
      if (rem[i] == remainder) { loop = i; goto looped; }
    rem[r] = remainder; x %= y; x *= 10; quo[r++] = x / y;
    if (r > DIGITMAX) break;
    continue;
    looped: break;
  }
  if (loop) {
    for (i = 1; i < r; i++) {
      if (i == loop) printf("["); printf("%d", quo[i]); if (i == r - 1) printf("]");
    }
  } else if (r <= DIGITMAX)
    for (i = 1; i < r; i++) printf("%d", quo[i]);
  else {
    for (i = 1; i < DIGITMAX; i++) printf("%d", quo[i]);
    printf("...");
  }
  puts("");
}
int main(void) {
  int x, y, i;
  recurringDecimal(1, 1);
  recurringDecimal(1, 3);
  recurringDecimal(2, 3);
  recurringDecimal(1, 8);
  printf("  "); for (i = 1; i < DIGITMAX; i++) printf("%d", i % 10); puts("");
  recurringDecimal(1, 991);
  recurringDecimal(1, 997);
  recurringDecimal(10, 89);
  recurringDecimal(1234, 555);
  puts("分子 分母 を正数で入力してください。");
  scanf("%d%d", &x, &y);
  if (x < 0) x = -x;
  if (y < 0) y = -y;
  printf("%d / %d = ", x, y);
  recurringDecimal(x, y);
  return 0;
}