- it
- 古典密码之凯撒密码
#include <stdio.h>
#include <stdlib.h>
#include<string.h>
int main
(){
char s
[26]={'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};
char b
[26]={'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};
char result
[1000];
char a
[1000];
char c
;
int i
,l
,count
=0,t
=0,k
,p
;
int f
,h
;
flag2
: printf("凯撒密码加解密:\n请输入字母文本:\n");
gets(a
);
l
=strlen(a
);
for(i
=0;i
<l
;i
++)
{
if(((a
[i
]>='a'&&a
[i
]<='z')||(a
[i
]>='A'&&a
[i
]<='Z'))&&(l
<=1000))
{
t
++;
}
else
{ count
++;
}
}
if(count
>0)
{ printf("输入错误或超过输入范围！请重新输入！\n");
count
=0;
goto flag2
;
}
printf("\n");
flag3
:printf(" 1:加密\n 2:解密\n 3.结束\n");
h
=scanf("%d",&f
);
if(h
==1)
{
if (f
== 1)
{
flag1
: printf("Input the Key(1~26):" );
if(scanf("%d",&k
)==1)
{
if (k
>0&&k
<=26)
{
for(i
=0;i
<l
;i
++)
{
if(a
[i
]>='A'&&a
[i
]<='Z')
{
result
[i
]=b
[((a
[i
]-'A')+k
)%26];
}
else if (a
[i
]>='a'&&a
[i
]<='z')
{
result
[i
]=s
[((a
[i
]-'a')+k
)%26];
}
else result
[i
]=a
[i
];
printf("%c",result
[i
]);
}
printf("\n\n");
goto flag3
;
}
else
{
printf("Please Input 1~26!\n");
goto flag1
;}
}
else
{
printf("输入错误！请重新输入！\n");
fflush(stdin);
goto flag1
;}
}
else if (f
== 2){
for (k
=1;k
<=26;k
++)
{printf("k=%d，",k
);
for(i
=0;i
<l
;i
++){
if(a
[i
]>='A'&&a
[i
]<='Z')
{
p
=((a
[i
]-'A')-k
);
while(p
<0)p
+=26;
result
[i
]=b
[p
];
}
else if (a
[i
]>='a'&&a
[i
]<='z')
{
p
=((a
[i
]-'a')-k
);
while(p
<0)p
+=26;
result
[i
]=s
[p
];
}
else result
[i
]=a
[i
];
printf("%c",result
[i
]);
}
printf("\n");
}
printf("\n\n");
goto flag3
;
}
else (f
== 3);
{
goto flag4
;
}
}
else
{
printf("没有这个选项！请重新输入!\n");
fflush(stdin);
goto flag3
;
}
flag4
:return 0;
}
