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 * * *    *  * *  
int main(){
 **   ** *  *  ** *   ******   *temp;
***   * **   *   * *** *    *     * *str1 = ***      ***   *
 *    * ****        ***  * *  ** *** *str2 =   * *    everything  ** *   * *
*** **  *  *   ****   ****    ****  = str1;
   **** *    ** **    ***** * = str2;
 * * *    *    ** *** *** ***   = temp;
* ***  *       * **** *** *  * **  *  **** **    * * str1, str2);
* * **  * *******      *   ***** * 0;
}

Comments

Case 0: Correct output

Answer 2

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

Comments

Case 0: Correct output

Answer 3

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

Comments

Case 0: Correct output

Answer 4

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

Comments

Case 0: Correct output

---

If you declare as a char array, you must  use array in the code

Answer 5

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

Comments

Case 0: Wrong output

---

-----------Re-judge-----------
Case 0: Correct output

---

We have to use point, instead of using array.

Answer 6

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

Comments

Case 0: Wrong output

---

-----------Re-judge-----------
Case 0: Correct output

Answer 7

Hidden content!
#include ****    *****
void **   *str1, char *str2)
 ** * ** *   *** *  *** are attached to the swap function
{
 **    * **          ***   *  * *temp= str1;
 **  *** * *  *  *****   ****     
 *  *   * * ***  **      *   * *  
    **   **  *  ** swap   * * a pointer *temp was declared  *   *  to   * * *   ***
}



int main()
{
*  * *  ***    *****    * ***   **   ***  ****     *  **   *** *  
 *    ***** *  ****   * ***  *   *****  *   *   *  * ****** *  * ** **  
 *       ****  **  ** * ** * *   ** 
  ****  **   ****  *    ** i[7] =  ** ** *  *** *
*         *  *  * *  * char j[17] = ** *   ****  * ** ** ** 
***   * *  
   * **  ***** ** **    ** ** *  ** and swap again in the main  ***



*  * ****    ** ** * * ** * * ***
*  ***      *** *** * * * *    * * ** 
** *  * *  ***  * * ** ** ***** **  *  

* ** *       **** ****  **   * **** **  ** **    str1);
**  ** * * *****      * * * * **  0;
}

Comments

Case 0: Wrong output

---

-----------Re-judge-----------
Case 0: Correct output

---

Case 0: Correct output

---

Case 0: Correct output

Answer 8

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

Comments

Case 0: Wrong output

---

Case 0: Wrong output

---

-----------Re-judge-----------
Case 0: Correct output

---

"char str1[]" is to create a space to store the strings, and the "char *str1" is a pointer to point to the constant strings.

Answer 9

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

Comments

Case 0: Correct output

---

-----------Re-judge-----------
Case 0: Wrong output

---

Case 0: Correct output

Answer 10

Hidden content!
  ** *  * *  *  *   * 
int main()
{
     * ***  *  * ** * *  * * * *temp;
** *  ****  * ** *      ** * *  *str1 = *** *   * *   *   
** *  ** *   * ****   *** * *    *str2 =    ** * ***  *   * **   

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


***   **** **     ** can not * *  to *     * ***  
we need use **     which *   ** *   *   to ** * ** *** *  

Comments

prog.c:1:1: error: expected '=', ',', ';', 'asm' or '__attribute__' at end of input
 ccc
 ^~~

---

prog.c:1:1: error: expected '=', ',', ';', 'asm' or '__attribute__' at end of input
 ccc
 ^~~

---

prog.c: In function 'main':
prog.c:7:10: error: assignment to expression with array type
     temp = str1;
          ^
prog.c:8:10: error: assignment to expression with array type
     str1 = str2;
          ^
prog.c:9:10: error: assignment to expression with array type
     str2 = temp;
          ^

---

Case 0: Correct output