单表密码的C语言实现

#include

#include

#include

void Decryp( char str_Letter[], char str_Min[], char str_Mi[]
)

{

int i = 0, j
= 0;

for( ;
str_Min[i] != '\0'; i++ )

{



int index = str_Min[i] - 'a';



str_Mi[j] = str_Letter[index];



j++;

}

}

void ChangTable(char str_Letter[], char str_NewLetter[]
) //将明密文对偶表转换成密明文对偶表

{

int i =
0;

int OldIndex
= 0;

int NewIndex
= 0;

for( ; i
< 26; i++ )

{



OldIndex = i;



NewIndex = str_Letter[i] - 'a';



//OldIndex = i;



str_NewLetter[NewIndex] = OldIndex + 'a' ;

}

}

int menu()

{

int n =
1;


printf("\t\t1.加密
2.脱密
3.退出\n");


printf("请选择您的功能：");


scanf("%d",&n);

return
n;

}

int main( void )

{

static char
str_Min[100];

static char
str_Mi[100];

static char
str_Letter[26] = { 'a', 'c', 'b', 't', 'i', 'f', 'l', 'h', 'e',
'k', 'o', 'm', 'r', 'n', 'j', 'p', 's', 'g', 'q', 'd', 'u', 'v',
'w', 'z', 'y', 'x'};

char
str_NewLetter[26];

int n =
1;

label:

n =
menu();


getchar();


switch(n)

{

case
1:



printf("请输入明文：");



gets(str_Min);







Decryp( str_Letter, str_Min, str_Mi );



printf("密文：");



puts(str_Mi);



break;





case
2:



printf("请输入密文：");



gets(str_Min);



ChangTable( str_Letter, str_NewLetter );



Decryp( str_NewLetter, str_Min, str_Mi );



printf("脱密后的明文：");



puts(str_Mi);



break;

case
4:



exit(0);



break;






default:



printf("您的选择出错，按任意键退出程序！");



getchar();


exit(-1);



break;

}

goto
label;



return 0;

}