编码规则

Give an implementation of encoding a string which contains less than 20 chars. There three rules:

1. replace the alphabetical char in the string with the fourth char behind it, for example, a -> e ，A -> E， X -> B, y -> c, z -> d

2. if the char is not a alphabetical char, ignore it.

3. reverse the string updated

代码实现

static char lowerMap[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' \

};

static char upperMap[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' \

};

int encodeStr(char * str){

if(NULL == str){

printf("encodeStr param error\n");

return PARAM_ERR;

}

char * p = NULL;

int dist = 0;

p = str;

while('\0' != *p){

if(*p >= 'a' && *p <= 'z'){

dist = *p - 'a';

dist = dist + 4;

dist = dist % 26;

*p = lowerMap[dist];

} else if (*p >= 'A' && *p <= 'Z'){

dist = *p - 'A';

dist = dist + 4;

dist = dist % 26;

*p = upperMap[dist];

} else {

}

p++;

}

strReversWithWord(str);

return SUCCESS;

}

void testencodeStr(void){

char str[100] = "hasdxz11HYZ";

printf("\n************ testencodeStr ************ \n");

encodeStr(str);

printf("Encoded str is: %s\n", str);

return;

}

使用全局数组作为映射数组，同'a'或'A'的距离+4，作为数组下标；如果找过‘z’，通过取余的方式达到循环的目的

代码编译

gcc main.c str.c -g -o a.exe

调试输出

************ testencodeStr ************

Encoded str is: DCL11dbhwel