平成20年度春期試験_基本情報午後問10

h20h_fe_pm10.c

#include <stdio.h>
#include <ctype.h>

void tofraction(char *);
long power10(int);
long gcd(long, long);

void tofraction(char *str) {
  long numerator = 0;           /* 分子 */
  long denominator;             /* 分母 */
  int flag = 0;
  int n = 0;                    /* 準関節を除く小数部のけた数 */
  int k = 0;                    /* 準関節のけた数 */
  long measure;                 /* 分子と分母の最大公約数 */
  while (*str != '\0') {
    if (isdigit(*str)) {        /* 10進数字か? */
      numerator *= 10;
      numerator += *str - '0';
      if (flag == 1) n++;
      if (flag == 2) k++;
    } else if (*str == '.') {
      flag = 1;
    } else if (*str == '{') {
      flag = 2;
    }
    str++;
  }
  if (flag != 2) {              /* 有限小数又は整数の場合 */
    denominator = power10(n);
  } else {
    denominator = power10(n) * (power10(k) - 1);
    numerator -= numerator / power10(k);
  }
  measure = gcd(numerator, denominator);
  numerator /= measure;
  denominator /= measure;
  printf("= %ld/%ld\n", numerator, denominator);
}

long power10(int num) {
  long ret = 10;
  int i;
  if (num == 0) return 1;
  for (i = 1; i < num; i++) {
    ret *= 10;
  }
  return ret;
}

long gcd(long a, long b) {
  long tmp, r;
  if (a < b) {
    tmp = a;
    a = b;
    b = tmp;
  }
  r = a % b;
  while (r != 0) {
    a = b;
    b = r;
    r = a % b;
  }
  return b;
}

int main(void) {
  char *example[] = { "32",
                      "5.237",
                      "0.875",
                      "1.{3}",
                      "0.2{142857}" };
  int i, size = sizeof(example) / sizeof(example[0]);
  for (i = 0; i < size; i++) {
    printf("%s ", example[i]);
    tofraction(example[i]);
  }
  return 0;
}

平成20年度春季基本情報午後問10 - Mae向きなブログ