我的程序仅适用于大写字母,我无法解决问题。一切似乎都很好,但实际上并非如此。顺便说一句,这是CS50课程(第2周)的任务。 这是我的代码:
#include <stdio.h>
#include "cs50.h"
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
int main(int argc, string argv[])
{ /* Main should take only one parameter (except program execution, of course) */
if (argc != 2)
return 1;
string text = GetString(); // text to encrypt
int i, l = strlen(text);
int k = atoi(argv[1]); // shift value (key)
/* Shift value should be less or equal to 26 */
if (k > 26)
k = k % 26;
for (i = 0; i < l; i++)
{ /* Making sure the character to encrypt is a letter (from English alphabet) */
if ((islower(text[i])) || (isupper(text[i])))
{
if ((islower(text[i])) && ((text[i] + k) > 'z'))
text[i] = ('a' + text[i] + k - 'z' - 1);
if ((isupper(text[i])) && ((text[i] + k) > 'Z'))
text[i] = ('A' + text[i] + k - 'Z' - 1);
else
text[i] = text[i] + k;
}
printf("%c", text[i]);
}
printf("\n");
return 0;
}
结果
caesar.exe 13
HELLO WORLD hello world
URYYB JBEYQ uryyk sknyq
答案 0 :(得分:2)
整个街区;
if ((islower(text[i])) || (isupper(text[i])))
{
if ((islower(text[i])) && ((text[i] + k) > 'z'))
text[i] = ('a' + text[i] + k - 'z' - 1);
if ((isupper(text[i])) && ((text[i] + k) > 'Z'))
text[i] = ('A' + text[i] + k - 'Z' - 1);
else
text[i] = text[i] + k;
}
可以简化为:
if (islower(text[i]) || isupper(text[i]))
{
int base = islower(text[i]) ? 'a' : 'A';
int ord = text[i] - base; // normalize text[i] to be between [0-25]
ord = (ord + k) % 26; // rotate
text[i] = base + ord; // convert back to alphabet value
}