如何用函数解决字符串加密问题

void cryptograp(char ch[],int n)
{
int i;
for(i=0;i<n;i++){
if(ch[i]>='a'&&ch[i]<='z'){
if(ch[i]+5<='z')
return ch[i]+5;
else return (ch[i]+5)-'z'+96;
}
else if(ch[i]>='A'&&ch[i]<='Z'){
if(ch[i]+5<='Z')
return ch[i]+5;
else return (ch[i]+5)-'Z'+64;
}
else return ch[i];
}
}

#include <stdio.h>
void cryptograp(char ch[],int n)
{
    int i;
    for(i=0;i<n;i++){
        if(ch[i]>='a'&&ch[i]<='z'){
            if(ch[i]+5<='z')
                ch[i] = ch[i]+5;
            else ch[i] = (ch[i]+5)-'z'+96;
        }
        else if(ch[i]>='A'&&ch[i]<='Z'){
            if(ch[i]+5<='Z')
                ch[i] =  ch[i]+5;
            else ch[i] =  (ch[i]+5)-'Z'+64;
        }
    }
}
int main()
{
    char a[]={'a','c','m','d','p','s','d','b','q','\0'};

    printf("%s\n", a);

    cryptograp(a, 9);

    printf("%s\n", a);
    return 0;
}

运行结果为：