C语言编程问题，求高手解答遇到输入非法字符时，怎么处理。

C语言编程问题，求高手解答遇到输入非法字符时，怎么处理。

可以采用如下语句
while((scanf("%d",&x))==1)
{}
只有输入一个数字时，才进入主体语句

#include
#include
#include
#include "regex.h"

const int MAX_LEN = 1000;

char * trimString(char guessString[])
{
int head = 0 ,rear = strlen(guessString)-1;
char result[MAX_LEN];
int i,k;

while( guessString[head] != '\0' &&
(guessString[head] == ' ' || guessString[head] == ' ' )
)
{
head ++;
}


while( rear >= 0 &&
(guessString[rear] == ' ' || guessString[rear] == ' ' )
)
{
rear --;
}
for(i = head ,k = 0; i <= rear ; i++ , k++)
{
result[k] = guessString[i];
}
result[k] = '\0';

return result;
}


int transStringToNum(char guessString[])
{
int i;
int head = 0 ,rear = strlen(guessString)-1;
char trimGuessString[MAX_LEN];
int num = 0;
// 去前后空格
strcpy(trimGuessString,trimString(guessString));
// 检查是否空串
if( 0== strlen(trimGuessString) )
{
return -1;
}
// 检查是否有非数字字符
for(i = 0 ; trimGuessString[i] != '\0' ; i ++)
{
if(trimGuessString[i] < '0' || trimGuessString[i] > '9')
{
return -2;
}
}
// 字符串转换成数字
for(i = 0 ,num = 0 ; trimGuessString[i] != '\0' ; i++)
{
num = num * 10 + (trimGuessString[i] - '0');
}
return num;
}

int main()
{
int num,guessNum,n,count=0;
char guessString[MAX_LEN];
char reply;
srand(time(NULL));
do
{
//产生一个随即数
num=rand()%100+1;

printf("你有10次机会，请猜数字并按回车。\n");
for(n=1;n<=10;n++)
{

// 以字符串形式读入一个整数
gets(guessString);


guessNum = transStringToNum(guessString);
if(guessNum == -1 )
{
printf("请输入一个数字（必须是在1-100 之间）!\n");
n--;
continue;
}

if(guessNum == -2 )
{
printf("输入的不是一个合法数字（必须是在1-100 之间）!\n");
n--;
continue;
}

if(guessNum>num)
{
printf("It's too high!\n");
}
else if(guessNum {
printf("It's too low!\n");
}

else if(guessNum == num)
{
printf("You are right!\n");
printf("你共用了%d次机会猜对数字。\n",n);
break;
}
}

printf("Do you want to continue(Y/N or y/n)?");

fflush(stdin);
reply = getch();

}while((toupper(reply)=='Y'));
printf("The game is over!\n");
return 0;
}