问题描述
我有这个代码块(函数被省略,因为逻辑是家庭作业的一部分):
I have this block of code (functions omitted as the logic is part of a homework assignment):
#include <stdio.h>
int main()
{
char c = 'q';
int size;
printf("
Shape (l/s/t):");
scanf("%c",&c);
printf("Length:");
scanf("%d",&size);
while(c!='q')
{
switch(c)
{
case 'l': line(size); break;
case 's': square(size); break;
case 't': triangle(size); break;
}
printf("
Shape (l/s/t):");
scanf("%c",&c);
printf("
Length:");
scanf("%d",&size);
}
return 0;
}
前两个 Scanf 工作得很好,一旦我们进入 while 循环就没问题了,我有一个问题,当你应该被提示输入一个新的形状字符时,它反而跳到 printf
of Length 并等待从那里获取字符的输入,然后在循环的下一次迭代中输入小数.
The first two Scanf's work great, no problem once we get into the while loop, I have a problem where, when you are supposed to be prompted to enter a new shape char, it instead jumps down to the printf
of Length and waits to take input from there for a char, then later a decimal on the next iteration of the loop.
预循环迭代:
Scanf:形状.效果很好
Scanf:长度.没问题
Scanf: Shape. Works Great
Scanf: Length. No Problem
循环 1.
Scanf:形状.跳过这个
Scanf:长度.问题,这个 scanf 映射到形状字符.
Scanf: Shape. Skips over this
Scanf: length. Problem, this scanf maps to the shape char.
循环2
Scanf:形状.跳过这个
Scanf:长度.问题,这个 scanf 现在映射到大小 int.
Loop 2
Scanf: Shape. Skips over this
Scanf: length. Problem, this scanf maps to the size int now.
为什么要这样做?
推荐答案
scanf("%c")
从 键读取换行符.
scanf("%c")
reads the newline character from the key.
当你输入 15
时,你输入一个 1
,一个 5
,然后按 钥匙.所以现在输入缓冲区中有三个字符.scanf("%d")
读取 1
和 5
,将它们解释为数字 15
,但是换行符仍在输入缓冲区中.scanf("%c")
会立即读取这个换行符,然后程序会继续下一个 scanf("%d")
,并等待你输入一个数字.
When you type let's say 15
, you type a 1
, a 5
and then press the key. So there are now three characters in the input buffer. scanf("%d")
reads the 1
and the 5
, interpreting them as the number 15
, but the newline character is still in the input buffer. The scanf("%c")
will immediately read this newline character, and the program will then go on to the next scanf("%d")
, and wait for you to enter a number.
通常的建议是使用 fgets
读取整行输入,并在单独的步骤中解释每一行的内容.解决您当前问题的一个更简单的方法是在每个 scanf("%d")
之后添加一个 getchar()
.
The usual advice is to read entire lines of input with fgets
, and interpret the content of each line in a separate step. A simpler solution to your immediate problem is to add a getchar()
after each scanf("%d")
.
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