平成29年度秋季試験_基本情報午後問8

h29a_fe_pm8.c

#include <stdio.h>
#include <string.h>
#define N 30

const char tbl[N + 1] = " .,?abcdefghijklmnopqrstuvwxyz";

int getValue(char);
char getChar(int);
char calcCheckCharacter(char [], int);
int validateCheckCharacter(char [], int);

int getValue(char c) {
  int i;
  for (i = 0; i < N; i++) {
    if (tbl[i] == c) {
      break;
    }
  }
  return i;
}

char getChar(int i) {
  return tbl[i];
}

char calcCheckCharacter(char input[], int len) {
  int i, value, check_value, sum = 0; 
  int is_even = 0;
  for (i = len - 1; i >= 0; i--) {
    value = getValue(input[i]);
    if (is_even) {
      sum += value;
    }
    else {
      sum += (value * 2) / N + (value * 2) % N;
    }
    is_even = 1 - is_even;
  }
  check_value = (N - sum % N) % N;
  return getChar(check_value);
}

int validateCheckCharacter(char input[], int len) {
  int sum = 0, i, value;
  int is_odd = 1, ret_value = 1;
  for (i = len - 1; i >= 0; i--) {
    value = getValue(input[i]);
    if (is_odd) {
      sum += value;
    }
    else {
      sum += (value * 2) / N + (value * 2) % N;
    }
    is_odd = 1 - is_odd;
  }
  if (sum % N != 0) {
    ret_value = 0;
  }
  return ret_value;
}

int main(void) {
  char str[BUFSIZ] = "ipa  ", c;
  int len;
  len = strlen(str);
  c = calcCheckCharacter(str, len);
  str[len] = c;
  str[len + 1] = '\0';
  printf("%s\n", str);
  printf("ipa  f: %d\n", validateCheckCharacter(str, len + 1));
  printf("ケース1: %d\n", validateCheckCharacter("ipb  f", len + 1));
  printf("ケース2: %d\n", validateCheckCharacter("api  f", len + 1));
  printf("ケース3: %d\n", validateCheckCharacter("pia  f", len + 1));
  printf("ケース4: %d\n", validateCheckCharacter("  apif", len + 1));
  return 0;
}

平成29年度秋季基本情報午後問8 - Mae向きなブログ https://maehrm.hatenablog.com/entry/2019/03/13/212829