这是我的代码，我想输入字符串"adiva fiqri"；用键"；div"；但我希望关键是"；divdi vdivd"；(空格看起来像是字符串输入(，但我的新键在字符串后面(包括空格("；divdivdi"；
#include<stdio.h>
#include<string.h>
#include<ctype.h>
#include<stdlib.h>
void capital(int i, int j, char str[100]){
//converting entered string to Capital letters
for(i=0,j=0;i<strlen(str);i++)
{
str[j]=toupper(str[i]);
j++;
}
str[j]=' ';
return str[j];
}
int main()
{
int i,j,k,numstr[100],numkey[100],numcipher[100];
char str[100],key[100], newKey[100];
printf("Enter a string : ");
gets(str);
//converting entered string to Capital letters
/*
for(i=0,j=0;i<strlen(str);i++)
{
if(str[i]!=' ')
{
str[j]=toupper(str[i]);
j++;
}
}
str[j]=' ';
printf("Entered string is : %s n",str);
*/
capital(i, j, str);
printf("Entered string is : %s n",str);
//Storing string in terms of ascii
for(i=0;i<strlen(str);i++)
{
numstr[i]=str[i]-'A';
}
//masukan kunci
printf("Enter a key : ");
gets(key);
//converting entered key to Capital letters
for(i=0,j=0;i<strlen(key);i++)
{
key[j]=toupper(key[i]);
j++;
}
key[j]=' ';
//Assigning key to the string
for(i=0;i<strlen(str);)
{
for(j=0;(j<strlen(key))&&(i<strlen(str));j++)
{
numkey[i]=key[j]-'A';
i++;
}
}
//enkripsi
for(i=0;i<strlen(str);i++)
{
numcipher[i]=numstr[i]+numkey[i];
if(numcipher[i]>25)
{
numcipher[i]=numcipher[i]-26;
}
}
//generating new key
for(i = 0, j = 0; i < strlen(str); ++i, ++j){
if(j == strlen(key))
j = 0;
newKey[i] = key[j];
}
//hasil
printf("New Key : %s n", newKey);
printf("Vigenere Cipher text is : ");
for(i=0;i<strlen(str);i++)
{
printf("%c",(numcipher[i]+'A'));
}
printf("n");
}
这是我的代码，我想输入字符串"adiva fiqri"；用键"；div"；但我希望关键是"；divdi vdivd"；(空格看起来像是字符串输入(，但我的新键在字符串后面(包括空格("；divdivdi"；
关键是要理解您只对字母进行编码和解码。所有其他字符保持不变。键的大小写无关紧要，因为键只是表示字母表开头的偏移量。唯一的要求是，从一开始测量偏移量时，必须与情况保持一致。
对于任何给定的字符串，您应该只调用strlen()一次。如果需要保存长度，则创建一个变量，例如
size_t slen = strlen (str),
klen = strlen (key);
不需要在循环限制(例如for(i=0;i<strlen(str);i++)(中使用strlen()来迭代字符串。在C中，字符串以nul字符' '(例如普通的旧ASCII0(结尾。您所需要做的就是使用该字符作为测试进行迭代。当你到达nul终止字符时，循环将自行退出，例如
for (i = 0; str[i]; i++)
考虑到这一点，您可以按照Vigenère密码的描述来编写加密和解密实现。您可以将加密函数写成：
char *vigenere_encipher (char *cipher, const char *s, const char *key)
{
char *ci = cipher;
const char *k = key;
while (*s && *s != 'n') {
/* works encoding from upper or lower regardless of key case
* due to key char representing offset from beginning of alphabet
* in either case.
*/
if (isalpha (*s)) { /* only encodes and decodes Letters */
if (islower (*s))
*ci++ = (tolower (*k) - 'a' + *s - 'a') % 26 + 'a';
else if (isupper (*s))
*ci++ = (toupper (*k) - 'A' + *s - 'A') % 26 + 'A';
k++;
if (!*k)
k = key;
}
else /* non-Letters remain unchanged */
*ci++ = *s;
s++;
}
*ci = 0;
return cipher;
}
你的解密功能是：
char *vigenere_decipher (char *s, const char *cipher, const char *key)
{
char *de = s;
const char *k = key;
while (*cipher) {
if (isalpha(*cipher)) { /* only encodes and decodes Letters */
if (islower (*cipher)) {
int off = *cipher - tolower (*k);
if (off >= 0)
*de = off % 26 + 'a';
else
*de = off + 26 + 'a';
}
else if (isupper (*cipher)) {
int off = *cipher - toupper (*k);
if (off >= 0)
*de = off % 26 + 'A';
else
*de = off + 26 + 'A';
}
k++;
if (!*k)
k = key;
}
else /* non-Letters remain unchanged */
*de = *cipher;
de++, cipher++;
}
*de = 0;
return s;
}
如果你愿意，你可以用数组索引代替指针的使用(例如，使用索引为i和k[i]的for循环，而不是使用指向当前字符的指针——由你决定。我发现，当字符串末尾达到nul字符时，只使用指针迭代到*ptr == 0;更容易。(与使用ptr[i]相同(
一个完整的示例，其中将key作为第一个参数传递给程序(如果没有给定参数，则默认为"LEMON"——以匹配上面链接中的示例(。提示用户输入要加密/解密的字符串：
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#define MAXC 1024
char *vigenere_encipher (char *cipher, const char *s, const char *key)
{
char *ci = cipher;
const char *k = key;
while (*s && *s != 'n') {
/* works encoding from upper or lower regardless of key case
* due to key char representing offset from beginning of alphabet
* in either case.
*/
if (isalpha (*s)) { /* only encodes and decodes Letters */
if (islower (*s))
*ci++ = (tolower (*k) - 'a' + *s - 'a') % 26 + 'a';
else if (isupper (*s))
*ci++ = (toupper (*k) - 'A' + *s - 'A') % 26 + 'A';
k++;
if (!*k)
k = key;
}
else /* non-Letters remain unchanged */
*ci++ = *s;
s++;
}
*ci = 0;
return cipher;
}
char *vigenere_decipher (char *s, const char *cipher, const char *key)
{
char *de = s;
const char *k = key;
while (*cipher) {
if (isalpha(*cipher)) { /* only encodes and decodes Letters */
if (islower (*cipher)) {
int off = *cipher - tolower (*k);
if (off >= 0)
*de = off % 26 + 'a';
else
*de = off + 26 + 'a';
}
else if (isupper (*cipher)) {
int off = *cipher - toupper (*k);
if (off >= 0)
*de = off % 26 + 'A';
else
*de = off + 26 + 'A';
}
k++;
if (!*k)
k = key;
}
else /* non-Letters remain unchanged */
*de = *cipher;
de++, cipher++;
}
*de = 0;
return s;
}
int main (int argc, char **argv) {
char buf[MAXC] = "",
cipher[MAXC] = "",
*key = argc > 1 ? argv[1] : "LEMON",
decode[MAXC] = "";
fputs ("input : ", stdout);
if (!fgets (buf, MAXC, stdin)) {
fputs ("(user canceled input)n", stderr);
return 1;
}
printf ("key : %sn"
"cipher: %sn", key, vigenere_encipher (cipher, buf, key));
printf ("decode: %sn", vigenere_decipher (decode, cipher, key));
}
示例使用/输出*
使用维基百科示例：
$ ./bin/vcipher_fn
input : ATTACKATDAWN
key : LEMON
cipher: LXFOPVEFRNHR
decode: ATTACKATDAWN
使用您的示例：
$ ./bin/vcipher_fn div
input : adiva fiqri
key : div
cipher: dldyi alyml
decode: adiva fiqri
仔细看看，如果你还有问题，请告诉我。