char str[] = "Hello World! 123";
int alphabets = 0, digits = 0, spaces = 0, special = 0;
for (int i = 0; str[i] != '\0'; i++) {
else if (isdigit(str[i])) {
else if (isspace(str[i])) {
printf("字母: %d\n", alphabets);
printf("数字: %d\n", digits);
printf("空格: %d\n", spaces);
printf("特殊字符: %d\n", special);