Question

我正在从书中做以下程序，并且不知道我在哪里出错了。有人可以向我指出一些我错过的逻辑错误吗？

开发一个程序，输入用于每个容量的里程驱动和加仑。该程序应计算并显示每个容器获得的每加仑英里数。在处理完所有输入信息后，程序应计算并打印所有储罐的每加仑组合里程数。

#include <stdio.h>

int main(void) {
    int total = 0, count = 0;
    float gallons_used, mpg, miles;
    while(gallons_used != -1) {
    printf("Enter the gallons used (-1 to end): ");
        scanf("%f", &gallons_used);
        printf("Enter the miles driven: ");
        scanf("%f", &miles);
        mpg = miles / gallons_used;
        printf("Miles / gallon for this tank was %f\n", mpg);
        total += mpg;
        count++;
    }
    total /= count;
    printf("Average miles to the gallon was: %d\n", total);
    return 0;
}

现在，看起来我的循环恰到好处，直到我退出它的值为-1，因为它仍然要求该坦克的里程数，显然输入它完全抛弃了总数。端。

Answer 1

你可以使用无限循环并在以下情况下将其分解（如果gallons_used = -1

）

for(;;) { // <-- infinite loop
    printf("Enter the gallons used (-1 to end): ");
    scanf("%f", &gallons_used);
    if (gallons_used == -1)
        break; // <-- exit the loop
    printf("Enter the miles driven: ");
    scanf("%f", &miles);
    mpg = miles / gallons_used;
    printf("Miles / gallon for this tank was %f\n", mpg);
    total += mpg;
    count++;
}

Answer 2

while(true) {
printf("Enter the gallons used (-1 to end): ");
    scanf("%f", &gallons_used);
    printf("Enter the miles driven: ");
    scanf("%f", &miles);
    if(gallons_used== -1 )break;
    mpg = miles / gallons_used;
    printf("Miles / gallon for this tank was %f\n", mpg);
    total += mpg;
    count++;
}

Answer 3

#include <stdio.h>

int main(void) {
    int total = 0, count = 0;
    float gallons_used, mpg, miles;
    while(gallons_used != -1) {
    printf("Enter the gallons used (-1 to end): ");
        scanf("%f", &gallons_used);
        if (gallons_used < 0)             // check gallons_used
            break;
        printf("Enter the miles driven: ");
        scanf("%f", &miles);
        mpg = miles / gallons_used;
        printf("Miles / gallon for this tank was %f\n", mpg);
        total += mpg;
        count++;
    }
    total /= count;
    printf("Average miles to the gallon was: %d\n", total);
    return 0;
}

Answer 4

您正在使用gallons_used未初始化。使用未初始化的变量会调用未定义的行为。在while的条件表达式中进行比较之前，您需要先对其进行初始化。你可以这样做

printf("Enter the gallons used (-1 to end): ");
scanf("%f", &gallons_used);           // Reading value for gallons_used

while(gallons_used != -1) {
    printf("Enter the miles driven: ");
    scanf("%f", &miles);
    mpg = miles / gallons_used;
    printf("Miles / gallon for this tank was %f\n", mpg);
    total += mpg;
    count++;
    printf("Enter the gallons used (-1 to end): ");
    scanf("%f", &gallons_used);
}

有人能向我指出一个小的逻辑错误吗？

4 个答案: