检测 scanf 读取的值的变化

Question

对于作业，我们应该从文本文档中读取日期和相关值（温度）的列表。每行中的值以逗号分隔。

示例数据：

dd,mm,yyyy,x,y,z,w
01,01,2011,1.1,5.2,6.5,7.5
02,01,2011,2.1,5.2,6.1,1.1
03,01,2011,4.5,2.5,6.1,2.1
...
30,01,2011,4.1,6.1,6.1,2.1
01,02,2011,2.5,6.1,7.1,6.3

到目前为止，我已经实现了一个循环来读取每一行：

while(scanf("%d,%d,%d,%f,%f,%f,%f", &dd, &mm, &yyyy, &x, &y, &z, &w) == 7)
{
}

我们假设文档中没有错误，并且没有重复的日期。

但是，可能会缺少条目（并非每个月都有完整的数据；缺少日期）。

我无法检测每个月的数据 (mm) 是完整的月份还是仅部分月份。

例如：2011 年 3 月有 31 天。如果我从 3 月开始有 31 个条目，我需要打印“完整月份”，否则如果缺少天数，我必须打印“部分月份”。

到目前为止，我一直在使用 if(mm==1){} 语句在 while(scanf(...)) 循环内分隔每个月，然后递增它们在单独的变量中，然后将其与完整月份的天数进行比较，但我不知道如何实现它，因此它检测到 mm 已从上一行（新月份）更改并执行特定操作（例如：计算）

抱歉，如果这令人困惑！

我们还没有学过数组，只学过运算、循环和函数。

Answer 1

首先，我认为您不需要不同月份的“单独变量”。为什么不是一个按月份（即 mm）索引的数组？这可能会将您的代码长度减少一个数量级。哦，你还没有学过数组。

其次，在循环的顶部设置一个“last_mm”变量。这将是上次循环时 mm 的值。将其初始化为-1或其他值。当last_mm和mm不同时，你就知道月份已经改变。在循环的底部，将 last_mm 设置为 mm。

一般来说，这是检测循环期间变化的方法。

Answer 2

将上个月的值保留在某处；当您正在读取的月份高于上个月时，完成每月相关计算并重置每月计数器

int curmonth = 1;
int dd,mm,yyy;
float x,y,z,w;
float xtotal = 0,ytotal = 0,ztotal = 0,wtotal = 0;
while(scanf("%d,%d,%d,%f,%f,%f,%f", &dd, &mm, &yyyy, &x, &y, &z, &w))==7 {
    if (mm == curmonth) {
        //add to current counters
        ztotal+=z;
        ytotal+=y;
        xtotal+=y;
        wtotal+=w;
    } else {
        if (mm < curmonth) 
            //not the expected order as per specs so better die now
            exit(1);
        printf("month=%d,my_calculations=%f,%f,%f,%f\n",xtotal,ytotal,ztotal,wtotal);
        xtotal = ytotal = ztotal = wtotal = 0; curmonth=mm;
    }
} 

Answer 3

以下代码未经测试，但类似的代码应该可以在没有数组的情况下为您解决问题。我希望你已经知道 switch/case 了。

//Keep track of which month we are fetching data for
int currentMonth = 1;
//Number of days for which data have been read for the current month
int numberOfDaysInCurrentMonth = 0;
//Full = 1 would represent if all data is available for currentMonth
int full = 0;
//This is set to 1 only when data is read for a month different to currentMonth
int monthChanged = 0;

while(scanf("%d,%d,%d,%f,%f,%f,%f", &dd, &mm, &yyyy, &x, &y, &z, &w) == 7)
{
    // If month changed in last iteration  
    if(monthChanged == 1) {
        //Check if full = 1 print "Full Month" to output
        if(full == 1) {
             printf("Full Month");
        //Else there was partial data 
        } else {
             printf("Partial Month");
        }

        //Once the output is on the screen set this back to 0, so it will be set to 
        //1 only when month changes next time.
        monthChanged = 0;
    }

    //If currentMonth is the same as mm, just add 1 to number of days in this month
    //for which data is provided  
    if(currentMonth == mm) {
        ++numberOfDaysInCurrentMonth;

    //otherwise
    } else { 
        switch(currentMonth) {
            //In case the month is January, March, May, July, August, October, December
            case 1, 3, 5, 7, 8, 10, 12:
                //Number of days should be 31 for full to be 1
                if(numberOfDaysInCurrentMonth == 31)
                     full = 1;
            break;
            //In case the month is February
            case 2:
                //Number of days should be 28 for month to be full 
                //(ignoring leap years)  
                if(numberOfDaysInCurrentMonth == 28)
                     full = 1;
            break;
            //In case the month is April, June, September, November
            case 4, 6, 9, 11:
                //Number of days should be 28 for month to be full 
                if(numberOfDaysInCurrentMonth == 30)
                     full = 1;
            break;     
        }
        //Now that we have set what we desired, set
        //currentMonth to mm 
        currentMonth = mm;
        //The month just changed, otherwise we would not have been in this part
        of the code
        monthChanged = 1;
        //Number of days in current month starts from 1
        numberOfDaysInCurrentMonth = 1;
    }

    //Do whatever you are doing with data here
}