如何防止系统将前哨值作为输入？

问题描述

因此，我创建了一个简单的程序供用户输入温度并计算最高，最低，平均值。用户输入哨兵值停止循环后，不知何故哨兵值也将作为输入并弄乱数据，这是我的代码，请帮我看看您是否有空，谢谢！

#include <stdio.h>

int main()
{
    int temperature,highest = 0,lowest = 0,counter = 1,counter2 = 0,total = 0;
    float average;
    
    printf("Enter temperature (-999 to stop) > ");
    scanf("%d",&temperature);
    
    if (temperature == -999) {
    printf("No temperature is captured.");
    return 0;
    }
    
    else if (temperature > 40)
    counter2++;
    
    do {
        printf("Enter temperature (-999 to stop) > ");
        scanf("%d",&temperature);
        
        if (temperature >= highest)
        highest = temperature;
        
        if (temperature <= lowest)
        lowest = temperature;
        
        if (temperature > 40)
        counter2++;
        
        total += temperature;
        counter++;
    } while (temperature != -999);
    
    average = total / counter;
    
    printf("Total days with temperature more than 40'C > %d\n",counter2);
    printf("The lowest temperature  > %d\n",lowest);
    printf("The highest temperature > %d\n",highest);
    printf("Average of temperature  > %.2f\n",average);
}

解决方法

您的代码过于复杂。为什么您要从回路中输入第一个温度？第一个输入没有什么特别的。

您想要这样的东西：

#include <stdio.h>

int main()
{
  int temperature,highest = 0,lowest = 0,counter = 1,counter2 = 0,total = 0;
  float average;

  do {
    printf("Enter temperature (-999 to stop) > ");
    scanf("%d",&temperature);

    if (temperature == -999)
      break;

    if (temperature >= highest)
      highest = temperature;

    if (temperature <= lowest)
      lowest = temperature;

    if (temperature > 40)
      counter2++;

    total += temperature;
    counter++;
  } while (temperature != -999);

  average = total / counter;

  printf("Total days with temperature more than 40'C > %d\n",counter2);
  printf("The lowest temperature  > %d\n",lowest);
  printf("The highest temperature > %d\n",highest);
  printf("Average of temperature  > %.2f\n",average);
}

仍然存在一些错误，如果根本不输入温度，则该程序将无法正常运行。但是我让你自己一个。应该不难。

,

您添加了哨兵（-999），因为您在之前添加了值，然后到达了测试哨兵值的代码。您需要立即进行测试。

但是即使已解决，仍然存在更多问题。

您首先将lowest设置为零，因此，如果我输入20后接-999，那么lowest仍将为零。

您不保存第一个输入（递增count2除外），因此最终结果将是错误的。同样，如果我输入20后跟-999，那么total将为零（假设我们已经解决了哨兵问题）。如果我输入20 40 -999，则total只会增加40，而平均值将是20，因为count会增加两次。

此外，您应始终检查scanf返回值。

因此，您需要重新组织代码。例如：

#include <stdio.h>

int main()
{
    int temperature,counter = 0,total = 0;
    float average;
    
    printf("Enter temperature (-999 to stop) > ");
    if (scanf("%d",&temperature) != 1) exit(1);
    
    if (temperature == -999) {
    printf("No temperature is captured.");
    return 0;
    }
    
    lowest = temperature;
    highest = temperature;

    do {
        
        if (temperature >= highest)
        highest = temperature;
        
        if (temperature <= lowest)
        lowest = temperature;
        
        if (temperature > 40)
        counter2++;
        
        total += temperature;
        counter++;

        printf("Enter temperature (-999 to stop) > ");
        if (scanf("%d",&temperature) != 1) exit(1);
    } while (temperature != -999);
    
    average = total / counter;
    
    printf("Total days with temperature more than 40'C > %d\n",counter2);
    printf("The lowest temperature  > %d\n",lowest);
    printf("The highest temperature > %d\n",highest);
    printf("Average of temperature  > %.2f\n",average);
}