caser.c

凯撒密码-扩展的凯撒密码

#include<stdio.h>

//#include<ctype.h>
main()
{
    int i,key;
    int lenP;
    char pt[50];
    char ct[50];
     printf("                      caser\n");
    printf("*******************************************************\n");
    printf("please enter the word you want to protect:\n");
    gets(pt);
    printf("please enter your key:\n");
    scanf("%d",&key);
    printf("Ciphertext:\n");
    
    lenP=strlen(pt);
    //for(i=0;i<lenp;i++)
    //if()
    //printf("%d",lenP);
    for(i=0;i<lenP;i++)
    {
    if(pt[i]>='A'&&pt[i]<='Z'){
         //ct[i]=pt[i]+32+key%26;
         pt[i] = pt[i] + 32;  //转化为小写字母
         //tolower(ct[i]);    //大小写转换
         ct[i] = (pt[i]-'a' + key)%26 + 'a';
    }
    else if(pt[i]>='a'&&pt[i]<='z'){
        //ct[i]=pt[i]-32+key%26;
        ct[i] = (pt[i]-'a' + key)%26 + 'a';
        ct[i] = ct[i] - 32;
        //toupper(ct[i]);
     }
    else
        ct[i]=pt[i];
    putchar(ct[i]);
    //printf("%c",ct[i]);
   }
   //printf("%s",ct);

    printf("\n\n\n");
}