c - 平均值不在嵌套for循环中计算

Question

我对这个问题很困惑。我的总距离计算不正确。我不确定这是因为我的循环设置不正确还是我做错了什么。我每次平均得到 -0。我在平均计算之前打印了 printf("total distance = %lf , dailyflights = %d\n", totaldistance, dailyflights); 以确定它是 totaldistance计算不正确，不是平均值。

所需输出的示例:

How many days has your dragon been practicing?
3

How many flights were completed in day #1?
2
How long was flight #1?
10.00
How long was flight #2?
15.00
Day #1: The average distance is 12.500.

How many flights were completed in day #2?
3
How long was flight #1?
9.50
How long was flight #2?
12.00
How long was flight #3?
13.25
Day #2: The average distance is 11.583.

How many flights were completed in day #3?
3
How long was flight #1?
10.00
How long was flight #2?
12.50
How long was flight #3?
15.00
Day #3: The average distance is 12.500.

我的代码:

//pre-processor directives
#include <stdio.h>

//Main function
int main()
{
    int days = 0, totaldays, flight_num, dailyflights;
    double distance, cur_distance = 0, totaldistance = 0, average_dist;

    printf("How many days has your dragon been practicing?\n");
    scanf("%d", &totaldays);

    for(days=1; days <= totaldays; days++) {
        printf("How many flights were completed in day #%d?\n", days);
        scanf("%d", &dailyflights);

        for (flight_num=1; flight_num <= dailyflights; flight_num++) {
            printf("How long was flight #%d?\n", flight_num);
            scanf("%ld", &distance);
            totaldistance = distance + totaldistance;
        }
        printf(" total distance = %lf , dailyflights = %d\n", totaldistance, dailyflights); /*I printed this line to determine what isn't correct and I determined that totaldistance is not calculating correctly*/
        average_dist = totaldistance / (float) dailyflights;
        printf("Day #%d: The average distance is %.3f.\n", days, average_dist);

    }

    return 0;
}

Answer 1

你必须使用 %lf 而不是 %ld 来读取 double 的值到 distance 扫描。

您应该使用 %f 而不是 %lf 来使用 printf 打印 double 的值 因为 float 值是自动扩展的，所以不需要区分它们。

此外，在内循环之前，您需要设置 totaldistance = 0.0;，这样您就可以将每天的航类与其他每天的航类分开累积，从而使平均距离计算正确。