作者nopicnic (nopicnic)
看板C_and_CPP
标题[问题] C语言FUNCTION的引数问题
时间Wed Sep 9 07:42:37 2009
不好意思，想请问板上先进一个问题。
该题CODE码是从课本复制而来
是一个使用指标函数的气泡排序法。
我的问题是其中swap函式的是void swap( int *element1Ptr, int *element2Ptr )
当我将函式定义及呼叫swap时所需要的引数都改成(int element1ptr , int element2ptr)
时:
将
void swap( int *element1Ptr, int *element2Ptr )
{
int hold; /* temporary holding variable */
hold = *element1Ptr;
*element1Ptr = *element2Ptr;
*element2Ptr = hold;
} /* end function swap */
改成
void swap( int element1Ptr, int element2Ptr )
{
int hold; /* temporary holding variable */
hold = element1Ptr;
element1Ptr = element2Ptr;
element2Ptr = hold;
} /* end function swap */
程式可以执行，但是却失去了排序的功能。
我不知道是自己哪里的观念出了问题...只能麻烦板上有空的板友请解答..谢谢。
下面是原本的CODE：
#include <stdio.h>
#define SIZE 10
/* prototypes */
void bubble( int work[], const int size,
int (*compare)( int a, int b ) );
int ascending( int a, int b );
int descending( int a, int b );
int main()
{
int order; /* 1 for ascending order or 2 for descending order */
int counter; /* counter */
/* initialize array a */
int a[ SIZE ] = { 2, 6, 4, 8, 10, 12, 89, 68, 45, 37 };
printf( "Enter 1 to sort in ascending order,\n"
"Enter 2 to sort in descending order: " );
scanf( "%d", &order );
printf( "\nData items in original order\n" );
/* output original array */
for ( counter = 0; counter < SIZE; counter++ ) {
printf( "%5d", a[ counter ] );
} /* end for */
/* sort array in ascending order; pass function ascending as an
argument to specify ascending sorting order */
if ( order == 1 ) {
bubble( a, SIZE, ascending );
printf( "\nData items in ascending order\n" );
} /* end if */
else { /* pass function descending */
bubble( a, SIZE, descending );
printf( "\nData items in descending order\n" );
} /* end else */
/* output sorted array */
for ( counter = 0; counter < SIZE; counter++ ) {
printf( "%5d", a[ counter ] );
} /* end for */
printf( "\n" );
return 0; /* indicates successful termination */
} /* end main */
/* multipurpose bubble sort; parameter compare is a pointer to
the comparison function that determines sorting order */
void bubble( int work[], const int size,
int (*compare)( int a, int b ) )
{
int pass; /* pass counter */
int count; /* comparison counter */
void swap( int *element1Ptr, int *element2ptr ); /* prototype */
/* loop to control passes */
for ( pass = 1; pass < size; pass++ ) {
/* loop to control number of comparisons per pass */
for ( count = 0; count < size - 1; count++ ) {
/* if adjacent elements are out of order, swap them */
if ( (*compare)( work[ count ], work[ count + 1 ] ) ) {
swap( &work[ count ], &work[ count + 1 ] );
} /* end if */
} /* end for */
} /* end for */
} /* end function bubble */
/* swap values at memory locations to which element1Ptr and
element2Ptr point */
void swap( int *element1Ptr, int *element2Ptr )
{
int hold; /* temporary holding variable */
hold = *element1Ptr;
*element1Ptr = *element2Ptr;
*element2Ptr = hold;
} /* end function swap */
/* determine whether elements are out of order for an ascending
order sort */
int ascending( int a, int b )
{
return b < a; /* swap if b is less than a */
} /* end function ascending */
/* determine whether elements are out of order for a descending
order sort */
int descending( int a, int b )
{
return b > a; /* swap if b is greater than a */
}
--
※ 发信站: 批踢踢实业坊(ptt.cc)
◆ From: 114.39.173.77
※ 编辑: nopicnic 来自: 114.39.173.77 (09/09 08:02)
1F：推 zinn:函式引数不用指标的话 他是复制一份local variable进去 09/09 08:18
2F：→ zinn:所以函式scope外面的值是不会变的 09/09 08:18
3F：→ nopicnic:感激!!突然了解~~因为之前都是自学没人点，真的很谢谢你 09/09 08:25
4F：推 VictorTom:卖一下瓜XD 本板文章编号 #1A5iL3A- 小弟写过解释:) 09/09 09:43
5F：→ nopicnic:我认真看完了，非常详细，谢谢你>"< 09/09 12:08
6F：推 shieldsky:我刚刚也看完，但有个疑问我po在V大的文章内，烦请解惑 09/09 20:32
7F：推 VictorTom:讨厌啦~~又暴露了人家英文不好这件事了啦....(羞) 09/09 20:59
8F：推 MaxHaru:call by value 跟 call by reference的不同.. 09/12 11:40