12-21 Lab exercise 3: Fix the program with basic Pointer

Question

In the following program, we want to stores two strings in two arrays, swaps them, and displays their new content. There some error. Please fix it and explain why and how in the comment after your answer.

#include <stdio.h>
int main(){
    char temp[100];
    char str1[100] = "Let see";
    char str2[100] = "Is everything OK?";
    temp = str1;
    str1 = str2;
    str2 = temp;
    printf("%s %s", str1, str2);
    return 0;
}

 

Answer 1

Hidden content!
#include ****  * *** *  
 **  *  ****  *** *  **   * 
void change(int *str1,int *str2);

int main(){
 * **** ***** *  **   *** *  temp[100];
* ***  *    *   ***  **   ** *  ** str1[100] =  **** **       * **
** ** * **     * *   ***   str2[100] =     *  ** everything   **  *** 


    * *   *** * **    *  **     ***   = str1;
 ****  ***   *********** *   = str2;
*  ****   * *  ****  * *  *   *     * = temp;
* *   **    ***   *     *   ** * * * * *
*  *   *** * * *  *** * **  *****
***   *** **  **  ****   * * *  ****
 * * * * **  *   * ***  *  ** *  *    ** **   str1, str2);
**  *  * ** * * ****  *** *  * * 0;
}

Comments

Case 0: Correct output

Answer 2

Hidden content!
#include  **   * ****  ***
int main(){
  *  ** ** * ** **** *  *** * **** *
  *****  *  * ***   *  ** * ****  *str1[100] = **  ** * ***   *  * *
**** *  ***** *  ** * *  **  **   *str2[100] =  ***** everything ** * *****
****** **  **** *** **  ***  = *str1;
  *******      *    *   *** ** *  = *str2;
**  *     *   * **   *** ** = *temp;
  * * **   **  * ** *  ***  ** *  * * *    ****   *str1, *str2);
***** *    ***    * * **** **  0;
}

Comments

Case 0: Correct output

Answer 3

Hidden content!
#include     *     *****
int main()
{
 ** **** * ** * *  * **  * * temp[100];
* **      *   * * **     * * *  * str1[100] = "Let * * *** *
    **    * *  **    **   * **  str2[100] = "Is everything     **  **
 *  * * ****    * * *** *** *   **          **
* * *** * ***** * * *****       * * ** = *** *  * ***
* *** * *** * ** *****     * *   * = *** * *   * * * 
* **** *** ** *** * ****** ** **   * = *  * **  **
**  * *   ******   **   **         = *p2;
**** **  ****    * **** *** ****** = *p3;
* ***  **    * ** *    * *** * = *p1;
****   ** **** ***   **  ***    **     ** %s", str1, str2);
*   ** ** *  ******  ** * **    0;
}

Comments

Case 0: Wrong output

Answer 4

Hidden content!
* **  *  *  ** * *   ***
int     
{
*        * ***   ** ***  **
 **     ** char ** *
    **  * *  *  char *   = * * *** **   *** *   *
   * ** * **   char    =  * **   ***  * *   * *** 
* *  *  ***   ** * temp = str1;
**** **    * *  ** str1 =    
*    *  * *    str2 = temp;

   *** *   ** /*
    *   *      *  char    **
  *   *  *  **** char *    * =    *** ** ** **** *
  * ***    * *   *  char *****   =  *  * *  ***   * **** * *****
     ** *  **  *  **  i = 0; i *  ***   100; i++)
 ** *   **  ** {
**  * *    **** * *  * ****  *    **  =  *  **
**        ******   * **  ******** *  *** = * ***
 * *  * ** * ****   * **  **    **** =       *
**** * *  *  }
** **   * ***  */
*   *   *  **  * ***   *  ** * *  **   *    *  ** *
*  *     *  **      * 0;
}

Comments

Case 0: Correct output

Answer 5

Hidden content!
#include  *  **  **   
int main(){
**  *****  *    *  **** ***   *   * *temp;
 *      *****  ***** ** *  * *str1 =      *  ** ***** 
*****    *   **** * *   *  *str2 =   * *   everything *      * 
*         **** ** * *   ** *  * = str1;
*  * * * ***   * ** * ** **** **** = str2;
   ** *        ***    ***** * = temp;
   **   ***  *** *   * ***    ****    **** ** str1, str2);
  *** ** * **  * *    ** * ***   0;
}

Comments

Case 0: Correct output

---

Case 0: Correct output

---

原型態為指標常數，其值不可更改；指標變數的值才能被更改

Answer 6

Hidden content!
#include      *    *   
int main()
{
***     * *  **  **  **     * * i;
* ** ****   char  *  *****
  ****** * **  **** ***  *  *** str1[100] =  ** **   **  *
** * ** ** *** ** *      *   ** *  str2[100] =  * *  **  everything * **     * *
** **  ** ** * * * **   *      *   ****  
   * **** **  **   * *     ** ** 
    ** **** * * * *** ***  * *   * *** *  * *      *  temp[i] = str1[i];
  ***  ***  ****  ****  ***   **  *** * *    str1[i] = str2[i];
* *  * * ** ** **  *** ****  ***  * *  ** **** str2[i] =      *** **  *** *  
***         }
* *  ***  *   *  
*  **   * ***** **  * ** *      **** *   **  * * str1, str2);
* ** ** * *  ** ***  **** **  * *  0;
}

Comments

Case 0: Correct output

Answer 7

Hidden content!
 **** *  * * *   *    *
int **  
* *   *  * * * ** *  * **   **** 
***  * **   * * ***   *     * * * =     **    ***
 *  *  *  **  *** *   *     * *  *str2 = ** *      * * *  ** ** *
**  ***    *  *****  *  ****  = ****
*   *** **  ***** *   ** **  * *   = str2;
  *  ***   * * *    ** *       = ** 
**** ***  *  *  *  **    *  *   ****    *     **** ***  * str1,  * 
****    *  *  *  * *****    * * *    *  0;

}
/* A name of **      * *  must be ****  by an  **  * Here in  *** code there was no   *  in front of ***         name */

Comments

Case 0: Wrong output

---

Case 0: Wrong output

---

Case 0: Correct output

Answer 8

Hidden content!
** *  * **** * *  **  *** 


int  **  *
 *  *****   **  **  *  * **   * *
** *   * ****    ** *  * ** * *str1 =  **  ***  *** * **
*      *    * * ** * **  ***    *str2 = **  ** *  *  *        *
  ** * * * **   * ** * ****   = str1;
    *   **    * *        * = str2;
***   *   **      **   * *   = temp;
** * * ** **** ***  ***    **  *** * **    *   *  * str1, * * 
 **** **       **  ** **    
 *  *** *  *  *** *****     * * ** 0;
}

/*
 ** ** char *   and  *****   *   into this array may *** ** due to white *
**  * we can    *** as char  **  *    *  
*/

Comments

Case 0: Correct output

Answer 9

Hidden content!
#include **   * * *****
   *   ** *****  **  *
void change(int *str1,int *str2);

int main(){
***  ****   *     **** *  *  ** ******  * 
    * ***     *  ***** **   str1[100] = * * *  *  * * 
**  *** ** *** * * * *  * str2[100] =   *****   everything  **  *  * 
   *  *  *  ****    ** **  * **  *  * **  **
 *  *** ****    **  * * **  *** *** *** *  
**  * *     **** *** * *** *  *   **  *
***  * ** * *    *  ****  **     *** ** **  * str1, str2);
     *     * *  *   ** *  *  0;
}

Comments

prog.c:1:1: error: unknown type name 'assignment'
 assignment to expression with array type
 ^~~~~~~~~~
prog.c:1:15: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'expression'
 assignment to expression with array type
               ^~~~~~~~~~
prog.c:1:15: error: unknown type name 'expression'

---

Case 0: Wrong output

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Case 0: Correct output

Answer 10

Hidden content!
#include  * *** ***   *** 
int main(){
 **   *  * *  *  * *     ** *temp;
* * *** **    ** * **  *   ** *str1 =  * **   *   * *  
  * *   *   * ******  *     *str2 =     * everything ** *    *
**** **           **  *  **** = str1;
 ** *** *   **  ** **  *** *  * = str2;
*****   **    **** *     * = temp;
 * **   *** **  *****  *           *    *** str1, str2);
 ***  * * ** ** ** * ****** * * * 0;
}

Comments

Case 0: Correct output