c - 为我的程序提供一点帮助 : infinite loop in the scanf

Question

我的程序获得 5 个等级并计算平均值和最大值。但是当我先输入字母而不是等级时，它会连续打印“无效”。当我在输入 int 值后输入一个字母时，它会停止进一步获取剩余值。有人可以解释我错在哪里吗？谢谢

#include <stdio.h>
#include <stdlib.h>


int main()
{
    int grade[5];
    int temp;
    int temp2 = 0;
    for(int i = 0; i <= 4; i++) //getting inputs
    {
        printf("enter grade= ");
        scanf("%i", &temp);
        if(temp <= 100 && temp >= 0)
            grade[i] = temp;
        else
        {
            printf("invalid\n");
            i--;
        }
    }

    //print array
    for(int i = 0; i <= 4; i++)
        printf("%i\n", grade[i]);

    //Average
    for(int i = 0; i <= 4; i++)
    {
        temp2 = temp2 + grade[i];
    }

    printf("avg is= %i\n", temp2 / 5);

    //Max
    int mx = grade[0];

    for(int i = 1; i <= 4; i++)
        if(mx < grade[i])
        {
            mx = grade[i];
        }
    printf("max is= %i", mx);

    return 0;
}

Answer 1

来自 scanf 手册页:

These functions return the number of input items successfully
matched and assigned, which can be fewer than provided for, or
even zero in the event of an early matching failure.

因此，当扫描失败时，您必须读取并抛出有问题的字符，否则它仍然会在缓冲区中。