能帮忙看一下吗?通过率50%,找不到问题在哪 #include<stdio.h> #include<ctype.h> int main() { char str[100]; int i=0,Letters=0,Digits=0,Others=0; scanf("%s",str); while(str[i]!='?') { if(isalpha(str[i])) { Letters++; } else if(isdigit(str[i])) { Digits++; } else Others++; i++; } printf("Letters=%d\nDigits=%d\nOthers=%d\n",Letters,Digits,Others); }</ctype.h></stdio.h>