每天練練手3.20

/*#include <stdio.h>
int main()
{
	void swap( int *p1,int *p2 );
	int a,b;
	int *pointer_1,*pointer_2;
		printf("please enter a and b:\n");
		scanf("%d%d",&a,&b);                  //用指針交換兩指
		pointer_1 = &a;
		pointer_2 = &b;
		if( a < b )
			swap( pointer_1,pointer_2 );
		printf("max=%d,min=%d\n",a,b);
		return 0;
}

void swap( int *p1,int *p2 )
{
	int temp;
	temp = *p1;
	*p1 = *p2;
	*p2 =temp;
}*/

/*#include <stdio.h>
int main()
{
	void swap( int p,int q );
	int a,b;
	scanf("%d%d",&a,&b);
    swap( a,b );
	printf("a=%d,b=%d",a,b);
	return 0;
}                                        //只交換了形參的值，但函數調用之後形參的值釋放

void swap( int p,int q )
{
	int temp;
	temp = p;
	p = q;
	q =temp;
}
*/

/*#include <stdio.h>
int main()
{
	void swap( int *p1,int *p2 );
	int a,b;
	int *pointer_1,*pointer_2,*p1=NULL,*p2=NULL;
		printf("please enter a and b:\n");
		scanf("%d%d",&a,&b);
		pointer_1 = &a;
		pointer_2 = &b;
		if( a < b )
			swap( &a,&b );
		printf("max=%d,min=%d\n",a,b);
		printf("*p1=%d,*p2=%d\n",*p1,*p2);

		return 0;                          //用指針交換了pointer_1和pointer_2的值而並未交換a，b的值
}

void swap( int *p1,int *p2 )
{
	int *temp;
	temp = p1;
	p1 = p2;
	p2 = temp;
}
*/