问题描述
这个尚未正常工作的C程序的目的是输出每个输入行
反转（所以如果用户输入''hello''，程序将输出
''olleh'' - 请假设这个stdout和stdin !!!）。
为什么h ** l不是这个工作，为什么会崩溃？ ！
#include< stdio.h>
#define MAXINPUT 256
void reverse（char [ ]，int）;
main（）
{
int c;
int number ;
char s [MAXINPUT];
int i;
for（i = 0;（i< MAXINPUT-1） ）&&（（c = getchar（））！=''\ n''）; i ++）{
s [i] = c;
+ +数字;
}
反向（s，数字）;
for（i = 0; i< = number; i ++）
putchar（s [i]）;
返回0;
}
void reverse（char s []， int num_elements）
{
int i，j;
for（i = 0，j = num_elements-1;（ I< = num_elements-1 ）&&（j> = 0）; i ++，j--）
s [i] = s [j];
}
桌面检查。这意味着：拿出一张纸，假装你是一台b
的电脑。记下所有对象的值，每个对象都在它自己的b / b
列的头部。假设你有五个元素：
代码s [0] s [1] s [2] s [3] s [4] nij
''我是谁？'''''''''''''''5'？ ？
放下左栏中的每个代码步骤，查看
代码对所有相关对象的值的影响。例如：
代码s [0] s [1] s [2] s [3] s [4] nij
''h'' ''''''''''''''''''5'？ ？
i = 0'''''''''''''''''''''''5 0？
j = n- 1'''''''''''''''''''''''''''5 5 4
i< = 4？是的。
j> = 0？是的。
s [i] = s [j]'''''''''''''''''''''''''''''5 5 4
等等。手动执行此操作 - 桌面检查 - 是一个非常宝贵的帮助来理解你实际写的是什么，而不是你认为的那个
写的。
- -
Richard Heathfield
Usenet是一个奇怪的地方 - dmr 29/7/1999
电子邮件：rjh在上面的域名（但显然放弃了www）
-Arthur
This not-yet-working C program''s aim is to output each input line
reversed (so if the user enters ''hello'', the program will output
''olleh'' - and please assume this stdout and stdin!!!).
Why the h**l isn''t this WORKING AND WHY DOES IT CRASH???!
#include <stdio.h>
#define MAXINPUT 256
void reverse(char[], int);
main()
{
int c;
int number;
char s[MAXINPUT];
int i;
for (i=0; (i<MAXINPUT-1) && ((c = getchar()) != ''\n''); i++) {
s[i] = c;
++number;
}
reverse(s, number);
for (i=0; i<=number; i++)
putchar(s[i]);
return 0;
}
void reverse(char s[], int num_elements)
{
int i, j;
for (i=0,j=num_elements-1; (i<=num_elements-1) && (j>=0); i++,j--)
s[i] = s[j];
}
Desk-check it. That means: get out a piece of paper, and pretend you''re a
computer. Write down the values of all objects, each at the head of its own
column. Assuming you have five elements:
Code s[0] s[1] s[2] s[3] s[4] n i j
''h'' ''e'' ''l'' ''l'' ''o'' 5 ? ?
Put down each code step in the left hand column, and look at the effect the
code has on the values of all the relevant objects. For example:
Code s[0] s[1] s[2] s[3] s[4] n i j
''h'' ''e'' ''l'' ''l'' ''o'' 5 ? ?
i = 0 ''h'' ''e'' ''l'' ''l'' ''o'' 5 0 ?
j = n-1 ''h'' ''e'' ''l'' ''l'' ''o'' 5 0 4
i <= 4? Yes.
j >= 0? Yes.
s[i]=s[j] ''o'' ''e'' ''l'' ''l'' ''o'' 5 0 4
and so on. Doing this by hand - "desk-checking" - is an invaluable aid to
understanding what you actually wrote, as opposed to what you thought you
wrote.
--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999
http://www.cpax.org.uk
email: rjh at above domain (but drop the www, obviously)
-Arthur
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