Question

我只是想确定我的公式是正确的，并且想看看是否有办法使高度一直为零，而这里的时间计数是我的代码，到目前为止，我已经使用了一些方法像高度这样的数字是10且速度是0，它将以0.0开始计时，以.25递增，高度将从10开始计时，但高度不会递减为零，并且在该时间停止于0.75我很抱歉，如果它混淆了我试图解释的内容，im混淆了我的自我

// Programmer:      Your Name
// Date:            Date
// Program Name:    The name of the program
// Chapter:         Chapter # - Chapter name
// Description:     2 complete English sentences describing what the program does,
//                  algorithm used, etc.

#define _CRT_SECURE_NO_WARNINGS // Disable warnings (and errors) when using non-secure versions of printf, scanf, strcpy, etc.
#include <stdio.h> // Needed for working with printf and scanf
#include <math.h>
int main(void)
{
    // Constant and Variable Declarations
    double startingHeight = 0.0;
    double heightBall = 0.0;
    double volicetyBall = 0.0;
    double ballTime = 0.0;
    double downTime = 0.25;
    double maxHeight = 0.0;
    double timeLast = 0.0;



    // *** Your program goes here ***
    do {
        printf("\n Enter initial height of the ball (in ft.): ");
        scanf("%lf", &startingHeight);

        if (startingHeight < 0) {
            printf("\t The initial height must be greater than or equal to 0");
        }


    } while (startingHeight < 0);

    do {
        printf("\n Enter initial velocity of the ball (in ft. per sec.): ");
        scanf("%lf", &volicetyBall);

        if (volicetyBall < 0) {
            printf("\t The initial velocity must be greater than or equal to 0");
        }

    } while (volicetyBall < 0);

    printf("\n");
    printf("Time\tHeight\n");
    if (startingHeight < 0 && volicetyBall > 0) {
        printf("%0.2f\t%0.1f\n", ballTime, startingHeight);
    }


    else {

        do {

            heightBall = startingHeight + volicetyBall * ballTime - 16 * pow(ballTime, 2);

            if (maxHeight < heightBall) {
                maxHeight = heightBall;
            }


            if (heightBall >= 0) {
                printf("%0.2f\t%0.1f\n", ballTime, heightBall);
                timeLast = ballTime;
            }

            ballTime = ballTime + downTime;
        } while (heightBall >= 0);

    }

    printf("\n The maximum height the ball will reach is %0.1f feet\n", maxHeight);
    printf("\n The time for the ball to reach the ground is %0.2f seconds\n", timeLast);

    printf("\n");



    return 0;
} // end main()

Answer 1

是的，它是C，但是C导致 Undefined Behavior 未能验证用户输入。如果用户在输入球高时滑行并击中'r'而不是'5'，在代码中会发生什么？

要防止无效输入并从无效输入中恢复，您需要检查输入功能的返回结果和空stdin任何有问题的字符 阅读，例如

    /* validate every input */
    if (scanf ("%lf", &startingHeight) != 1) {
        int c;
        fputs ("error: invalid input.\n", stderr);
        do  /* read offending chars until '\n' or EOF */
            c = getchar();
        while (c != '\n' && c != EOF);
        continue;
    }

尽管使用do .... while (...)，您只是跳到循环的结尾，而您的startingHeight < 0测试为false，然后跳到速度问题，最好是：

for (;;) {  /* loop continually until valid input */
    printf ("\n Enter initial height of the ball (in ft.): ");
    /* validate every input */
    if (scanf ("%lf", &startingHeight) != 1) {
        int c;
        fputs ("error: invalid input.\n", stderr);
        do  /* read offending chars until '\n' or EOF */
            c = getchar();
        while (c != '\n' && c != EOF);
        continue;
    }

    if (startingHeight < 0) {
        printf ("\t The initial height must be greater than or equal to 0");
        /* you should empty stdin here as well -- hint: create a function */
    }
    else
        break;
}

这样，您可以重新询问高度问题，直到您拥有有效的startingHeight >= 0。

其他形式，请勿使用printf输出单个字符，例如putchar或fputc所要用于的单个字符。

// printf ("\n");      /* replace this with... */
putchar ('\n');

此外，也不需要两个printf进行的两次puts调用（您不执行任何转换），例如

// printf("\n");
// printf("Time\tHeight\n");
puts ("\nTime\tHeight");

否则，除了正常的开始无法通过验证之外，您的表现还不错。

我想确保我的程序是正确的，这是C编程

1 个答案: