1. isalpha() //判断是否为字母
char ch;
isalpha(ch);//如果ch是'a'-'z' || 'A'-'Z'则返回true 否则false
2. strcmp()//比较字符串数组是否相等| string 可以直接用“==”来判断
char word[5] = "aaaa";
strcmp(word,"aaab");//相同输出0,不同输出1;
char ch;
isalpha(ch);//如果ch是'a'-'z' || 'A'-'Z'则返回true 否则false
char word[5] = "aaaa";
strcmp(word,"aaab");//相同输出0,不同输出1;