凯撒密码用C 编写(凯撒密码程序流程图)
凯撒密码用C 编写(凯撒密码程序流程图)
#include stdio.h
#include stdlib.h
#include string.h
const int MAX_N=200;
int main(int argc, char *argv[])
{
int i,j,p;
char text[MAX_N];
char alphabet[30];
char op[10];
while(1)
{
printf("1---输入密码表 2---退出\n");
gets(op);
if(strcmp(op,"1")==0)
{
printf("密码表：");
gets(alphabet);
while(1)
{
printf("1---加密 2---解密 3---返回\n");
gets(op);
if(strcmp(op,"1")==0 ||strcmp(op,"2")==0 )
{
printf("输入文本：");
gets(text);
for(i=0;text[i]!='\0';i++)
{
if((text[i]='a'text[i]='z') || (text[i]='A'text[i]='Z') )
{
if(strcmp(op,"1")==0)
{
p=text[i]='a'? (text[i]-'a'):(text[i]-'A');
text[i]=text[i]+ alphabet[p]-(p+'A');
}
else
{
for(j=0;;j++)
if(alphabet[j]==text[i]||alphabet[j]==(text[i]-('a'-'A')))
break;
text[i]= text[i]='a' ? (j+'a') :(j+'A');
}
}
}//for(i)
if(strcmp(op,"1")==0)
printf("加密后的文本为:" );
else
printf("解密后的文本为：");
printf("%s\n\n",text);
}
else if(strcmp(op,"3")==0)
{
printf("\n");
break;
}
else
{
printf("选择有误！请重新选择！\n");
}
}//while(1)
}
else if(strcmp(op,"2")==0)
{
exit(1);
}
else
{
printf("选择有误！请重新选择！\n");
}
}
return 0;
}
/*
输入样例
QWERTYUIOPASDFGHJKLZXCVBNM
Welcome to ZZSY2009!
输出样例
Vtsegdt zg MMLN2009!
*/
按照题目要求编写的用凯撒密码加密的C语言程序如下
#includestdio.h
int main(){
char s[80];
int offset,i;
fgets(s,80,stdin);
scanf("%d",offset);
for(i=0;s[i]!='\0';i++){
if('A'=s[i] s[i]='Z')
if(offset=0)
s[i]='A'+(s[i]-'A'+offset)%26;
else
s[i]='A'+(s[i]-'A'+26+offset%26)%26;
else if('a'=s[i] s[i]='z')
if(offset=0)
s[i]='a'+(s[i]-'a'+offset)%26;
else
s[i]='a'+(s[i]-'a'+26+offset%26)%26;
}
printf("%s\n", s);
return 0;
}
这个很简单嘛，用ASC 和 CHR 转换一下嘛
打开Vb，添加2个label控件，2个text控件 1个command按钮
代码如下：
Private Function f(ByVal a As String, k As Integer, n As Integer) As String
If ((Asc(a) = 65 And Asc(a) = 97) Or (Asc(a) = 97 And Asc(a) = 122)) And Len(a) = 1 Then '判断是否为一个字母
'利用公式计算
If Asc(a) = 65 And Asc(a) = 97 Then f = Chr((Asc(a) - 64 + k) Mod n + 64) '当为大写的时候
If Asc(a) = 97 And Asc(a) = 122 Then f = Chr((Asc(a) - 96 + k) Mod n + 96) '当为小写的时候
Else
f = "error" '若不满足要求，则返回错误
End If
End Function
Private Sub Command1_Click()
Dim strold As String
Dim strnew As String
Dim k As Integer
Dim n As Integer
Dim i As Long
Dim tmp As String
k = 3
n = 26
strold = Text1.Text '要加密的字符串
For i = 1 To Len(strold)
tmp = Mid(strold, i, 1)
tmp = f(tmp, k, n)
If tmp "error" Then
strnew = strnew + tmp
Else
MsgBox "字符串中含有非法字符"
Exit Sub
End If
Next i
Text2.Text = strnew
End Sub
Private Sub Form_Load()
Text1.Text = "PROGRAM"
Text2.Text = ""
Command1.Caption = "加密"
Label1.Caption = "源字符串："
Label2.Caption = "加密字符串："
End Sub
