字符的输入和输出 输入确认

每当我们进行输入的时候，我们都要想到是否需要处理剩余的垃圾输入，从而让它们不会影响到我们的后续输入！尤其是gechar和“回车符”一起使用的时候！

 

#include<stdio.h>
#define MAX 1000
#define MIN -1000

bool bad_limits(int start,int end,int low,int high);
int get_int();
double answer(int start,int end);

int main(void){
    int start;
    int end;
    double result;

    do{
        printf("Please Enter the start (EOF to quit)\n");
        start = get_int();
        printf("Please Enter the end (EOF to quit)\n");
        end = get_int();
        if(bad_limits(start,end,MIN,MAX)){
            printf("Please try again!\n");
            continue;
        }
        else{
            result = answer(start,end);
            printf("The answer is %lf\n",result);
        }
    }while(start !=0 || end != 0);
    printf("Bye\n");

    return 0;
}

int get_int(){
    int input;
    char ch;

    while(scanf("%d",&input) != 1){//如果输入有问题
        while((ch = getchar()) != '\n'){//丢弃该行中的所有输入
            putchar(ch);//并将这些垃圾值显示出来
        }
        printf(" is not an integer.\n");
    }
    return input;
}

double answer(int start,int end){
    double total = 0;
    int i;

    for(i=start;i<=end;i++){
        total += i * i;
    }
    return total;
}

bool bad_limits(int start,int end,int low,int high){
    bool not_good = false;//设置标记位

    if(start > end){
        printf("start too big!\n");
        not_good = true;
    }
    if(start <low || end >high){
        printf("another problem!\n");
        not_good = true;
    }
    return not_good;
}