#include "stdio.h"
int main (void)
{
   float gallons;
   int miles,i=0;
   float x,h,z=0;
   
   printf ("Enter the gallons used (-1 to end): ");
   scanf ("%f",&gallons);
   printf ("Enter the miles driven: ");
   scanf ("%d",&miles);
   
   while ( gallons != -1){
      x = miles/gallons;
      z += gallons;
      i += miles;
      
      printf ("The miles/gallons for this tank was %f\n\n\n",x);
      printf ("Enter the gallons used (-1 to end): ");
      scanf ("%f",&gallons);
      printf ("Enter the miles driven: ");
      scanf ("%d",&miles);
      
      
    }
   
    h = i / z;
    printf ("The overall average miles/gallons was %f",h);
   
   
   
   return 0;
  
}
在输入-1时会继续出现"Enter the miles driven: "，怎样才能让程序忽略这个print继续下个语句？各位帮帮忙，谢谢

[[it] 本帖最后由 huangruoxu 于 2008-12-10 11:39 编辑 [/it]]

if(gallons==-1)    break/*(continue)*/  ;

printf ("Enter the gallons used (-1 to end): ");
   scanf ("%f",&gallons);
   printf ("Enter the miles driven: ");加个/*   printf ("Enter the miles driven: ");*/就可以了啊
这行有用吗？我觉的没用啊
   scanf ("%d",&miles);

你输入-1时，后面的while语句里的东西都不执行的，有什么意义呢？
PS：如果真要输入-1后，不执行   printf ("Enter the miles driven: ");的话，
可以把它写在while语句里，不知道这样回答LZ满意否？

也就是：
  printf ("Enter the gallons used (-1 to end): ");
   scanf ("%f",&gallons);
   while ( gallons != -1){
      printf ("Enter the miles driven: ");
   scanf ("%d",&miles);
      x = miles/gallons;
      z += gallons;
      i += miles;

不是有用没用，也可以换个格式，但是这个一道题目的要求格式，上面这个程序在while语句中，题目要求输入-1后就直接计算h=i/z,但是我弄出的程序在输入-1后会出现Enter the miles driven: ，想不到怎么解决了，帮帮忙

还在吗，我昨天也做这题了，我在while语句的 printf ("Enter the miles driven: ");
      scanf ("%d",&miles);改成了，
if (gallons!=-1){
   printf ("Enter the miles driven: ");
   scanf ("%d",&miles);
}
输入-1之后就不会出现后边的了，但是最后的那个输出所有的平均数那里不对，我一会把我写的程序发过来你看下，别的都对，就是输入-1之后的结果是错误的，整数就对，小数就不对，整的我很郁闷

下边是我写的程序，看你的程序跟我写的应该是一道题，就是汽车加油的那个问题吧：
int main ()
{
    int miles;
    int total;
    int counter;
    float gallons;
    float s;
    float average;
    total=0;
    counter=0;
    printf ("Enter the gallons used (-1 to end):");
    scanf ("%f",&gallons);
    printf ("Enter the miles driven:");
    scanf ("%d",&miles);
    s = (float)  miles / gallons;
    printf ("The miles / gallon for this tank was %f\n\n",s);

    while (gallons!=-1)
    {
        counter += gallons;
        total += miles;
        printf ("Enter the gallons used (-1 to end):");
        scanf ("%f",&gallons);
        if (gallons!=-1)
            {
                printf ("Enter the miles driven:");
                  scanf ("%d",&miles);
                  s = (float)  miles / gallons;
                  printf ("The miles / gallon for this tank was %f\n\n",s);
            }
        else   
            {
                average = (float) total / counter;
                printf ("\nThe overall average miles/gallon was %f\n",average);
              }
    }

}
注释我没写，逻辑总是分不清楚，注释写不出来，但是我能明白，就是别人看着累点，不好意思了

我重新改了一下，按我说的那个就没问题，能出来结果，完全的正确，我可以肯定，但是我写的程序，那么写那里出问题了，为什么最后的平均值那里就是不对呢，希望有知道的大哥，高手们帮帮忙，看看是哪里出错误了，谢谢大家了！

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