c语言 - 从输出中排除用户的输入值

Question

>编写一个c程序，其目标是多次获取用户的输入，当用户输入特定的年龄时，循环停止并输出用户刚刚输入的所有值中的平均值，最小值和最大值;但是，在确定年龄的最大/最小/平均值时，程序必须忽略停止while循环的年龄。我只能使用一个循环。我遇到的唯一问题是输出。它不是忽略具体的年龄，给我不稳定的数字。这是我的一段编码：

 #include <stdio.h>
 int age, avAge, minAge, maxAge, sum;
 sum = 0;
//here is where I get the user input
    while (age != -1){
              printf("Please enter age: n");
              scanf("%d", &age);
//here is where I try to calculate the average
              sum += age;
              avAge = sum / age;
//here is where I placed restrictions on the ages the user can input
              if (age >= 0 && age <= 100)
                   printf("Nice try!n");
//here is where I try to get the largest/smallest in order
              if (age < minAge)
                   minAge = age;
              if (age > maxAge)
                   maxAge = age;
//here is where I output if the user inputs a 0
              else ( age == -1){
              printf("Smallest: %dn", minAge);  
              printf("Largest: %dn", maxAge);
              printf("Average: %dn", avAge)
  return 0;
  }

请原谅我的编码格式，我在手机上，因为我在我的计算机上运行一个卸载的 ubuntu。我只是想了解我应该使用什么来防止程序使用 0 作为 minAge。由于我只能使用一个循环，因此我认为我的选择是有限的。请记住，我在c很新，所以我对我的任何无知表示歉意。谢谢。

Answer 1

我认为无限循环在这里有一定程度的意义，我已经将您的打印结果语句移出了循环，因此它们仍然只会在用户完成输入年龄 s 后执行。我还更正了if (age >= 0 && age <= 100)以if (age < -1 && age > 100)并在使用之前正确初始化了所有变量，并添加了一些注释，如果您有任何其他问题，只需删除评论:)

#include <stdio.h>
#include <limits.h> // for INT_MAX 
int main(void) 
{
    int age, avAge = 0, minAge = INT_MAX, maxAge = 0, sum = 0, avgCounter = 1; // avgCounter is the amount of times the loop has ran
    while( 1 ) //infinite loop broken if age == -1
    {
        printf("Please enter age: n");
        scanf("%d", &age);
        if( age == -1 )
            break;   // exit loop
        else if (age < -1 && age > 100)
           printf("Nice try!n"); // could add continue here in order to not skew the min/max and average age variables.
        else if (age < minAge)
           minAge = age;
        else if (age > maxAge)
           maxAge = age;
        sum += age;
        avAge = sum / avgCounter;
        avgCounter++;
    } 
    printf("Smallest: %dn", minAge == INT_MAX? 0 : minAge); // incase the user enters -1 straight away  
    printf("Largest: %dn", maxAge);
    printf("Average: %dn", avAge);
}

注意：看到"不稳定的数字"的实际原因可能是由于未初始化的变量而导致的未定义行为，在尝试读取/使用它们之前，您必须始终确保它们已初始化。

Answer 2

编辑 ：当前代码中存在太多与逻辑和语法相关的小错误。以下代码按您的要求按预期工作。

 #include <stdio.h>
 int main(){
 int age, avAge, minAge, maxAge, sum;
 minAge = 100000 ; // some very large number
 maxAge = -1;   // initailize with min possible age
 sum = 0;
 int iteration = 0 ; // no. of times the loops run with valid input from user
    do{
              printf("Please enter age: , -1 to quit n");
              scanf("%d", &age);
              if (age >= 0 && age <= 100) {
                   printf("Nice try!n");
                   iteration ++; 
                   sum += age;
                   avAge = sum / age;   
                 if (age < minAge)
                   minAge = age;
                 if (age > maxAge)
                   maxAge = age;
              }
              else {
                printf("Smallest: %dn", minAge);  
                printf("Largest: %dn", maxAge);
                printf("Average: %dn", avAge);
                break ;
              }     
    }
    while( age > 0 && age <= 100) ;
    return 0;
  }

关于 ideone 的工作示例。

Answer 3

假设有效年龄在 (0, 100] 范围内，下面是一个实现：

#include <stdio.h>
int main(void) {
    int age, minAge, maxAge, sum, avAge;
    sum = 0;
    int i = 0;     // counts the number of ages read
    printf("Please enter age: ");
    while (scanf("%d", &age)) {
        // if age is in range (0, 100], consider valid
        //   and invalid otherwise
        if (age > 0 && age <= 100) {
            // calculate sum
            sum += age;
            // if this is the first loop round (i == 0), initialize
            //   both minAge & maxAge to 'age', since they
            //   don't yet have a valid value
            if (i == 0) {
                minAge = age;
                maxAge = age;
                ++i;
            } else {
                if (age < minAge) {
                    minAge = age;
                }
                if (age > maxAge) {
                    maxAge = age;
                }
                ++i;
            }
        } else if (age == 0) {
            // if age is zero, break/exit loop
            // zero can be changed to any invalid value (eg. -1)
            break;
        } else {
            printf("Nice try!n");
        }
        printf("Please enter age: ");
    }
    // calculate average (outside loop)
    // average = sum / number of ages read
    avAge = sum / i;
    // print summary
    printf("Smallest: %dn", minAge);
    printf("Largest: %dn", maxAge);
    printf("Average: %dn", avAge);
    return 0;
}