C - 循环时输入

Question

我正在尝试学习C,我写了一个小程序来计算各种形状的面积.这是源代码:

#include "stdafx.h"

struct entry
{
    float x;
    float y;
};

void square()
{
    printf("\nPlease enter the size of one of the square's sides\n");

    struct entry sq;
    scanf_s("%f\n", &sq.x);

    printf("\nThe area of the square is %.2f\n\n", sq.x * sq.x);
}

void rectangle()
{
    printf("\nPlease enter the length and breadth of the rectangle\n");

    struct entry rec;
    scanf_s("%f\n", &rec.x);
    scanf_s("%f\n", &rec.y);

    printf("\nThe area of the rectangle is %.2f\n\n", rec.x * rec.y);
}

void triangle()
{
    printf("\nPlease enter the width and height of the triangle\n");

    struct entry tri;
    scanf_s("Width: %f\n", &tri.x);
    scanf_s("Height: %f\n", &tri.y);

    printf("\nThe area of the triangle is %.2f\n\n", (tri.x * tri.y)/2);
}

void circle()
{
    printf("\nPlease enter the radius of the circle\n");

    struct entry circ;
    scanf_s("%f\n", &circ.x);

    printf("\nThe area of the circle is %.2f\n\n", 3.14 * circ.x * circ.x);
}


void main()
{
    int input = 0;

    do
    {
        printf("---Area of a Shape---\n\n");
        printf("1. Square\n");
        printf("2. Rectangle\n");
        printf("3. Triangle\n");
        printf("4. Circle\n");
        printf("5. Exit\n");
        printf("\n\n");

        printf("Please make a choice\n");
        scanf_s("%d", &input);

        switch(input)
        {
            case 1: square();
                    break;

            case 2: rectangle();
                    break;

            case 3: triangle();
                    break;

            case 4: circle();
                    break;

            case 5: printf("\n\nThank you for using this program!  Press enter to exit!\n");
                    break;

            default: printf("\nInvalid choice!\n\n");
                    break;
        }       
    }
    while(input != 5);

    getchar();
    getchar();
}

我对程序的唯一问题是,在输入边的大小以便计算区域之后,它等待我在显示答案之前输入另一个数字(进行选择).我不知道问题出在哪里.我认为在移动到另一个函数之前,C确保它执行手头的整个函数.你能帮我解决一下这个问题吗？谢谢.

Answer 1

在你的scanf格式中,

scanf_s("%f\n", &rec.x);

它'\n'不代表文字'\n',而是代表空白字符的任意序列.因此,在scanf_s您输入一个非空白字符后,调用不会结束(和空格)[输入可能不会发送到您的程序,直到您在此之后键入换行符].只需'\n'从格式中删除即可.