1.计数器方法size_t my_strlen(char* str){size_t count=0;assert(str);while(*str!='\0'){count++;str++;}return count;}2.指针方法int my_strlen(char* str){char* start = str;while (*str != '\0'){str++;}return str - start;}3.递归int my_strlen(char* str){if (*str == '\0')return 0;elsereturn 1 + my_strlen(str + 1);}