12-07 Exercise 2: Function num_digits

Question

Write a function num_digits(n) that returns the number of digits in n ( a positive integer). Hint: to determine the number of digits in a number n, divide it by 10 repeatedly. when n reaches 0, the number of divisions indicates how many digits n originally had.

寫一個num_digits(n)函數 計算n有幾位數

#include <stdio.h>
int num_digits(int n)
{
   /*INSERT YOUR CODE HERE*/

   /*在這裡寫你的程式*/
   /*END OF YOUR CODE*/
}

int main(void)
{
   int n;
   scanf("%d", &n);
   printf("%d has %d digit(s)",n,num_digits(n));
   return 0;
}

Please complete this program by only insert your code between those tags:

   /*INSERT YOUR CODE HERE*/ 
   /*END OF YOUR CODE*/

Example input

12347

Example output

12347 has 5 digit(s)

Remember: You may correct the cases, but your code always be revised!

Answer 1

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
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     *  *   *** * ** *    *** ** != 0)
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* ****   * **  ** *  * **   * *      *   ** *      *
** **  ** ****  **     ** *    *   *  * *  ** * ** ***  /= 10;
* *   ** * *****    **      * 
** * * * ** ** **      **   *  count;
}

int main(void)
{
* *   ** *** *     ***   ***  n;
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  *  **   **   ***   **  * *    **  * has %d ** *  ***** ** *   ** ***  
  **  **    *      ** **  * 0;
}

Comments

Case 0: Correct output
Case 1: Correct output
Case 2: Correct output
Case 3: Correct output

Answer 2

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
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}

int main(void)
{
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  ** ***** *  *  **   *****   *  *  has %d *  * * *  **       * * 
     * *  * *  ***  ** * * 0;
}

Comments

Case 0: Correct output
Case 1: Correct output
Case 2: Correct output
Case 3: Correct output

Answer 3

Hidden content!
#include ***  *  *    *
#include **   ** * ** ****
int num_digits(int n)
{
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*  * ***      **  *    * ** 1;
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**** *  * *  * *  * * * *  *  
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}



int main(void)
{
**  * **   **     ** * * n;
******    *    *    *  * **  **     *   &n);
 *  * *     * ***** * ** * * has %d * ** **  * *   *** *
** * * * ******   * *  * * 0;
}

Comments

prog.c: In function 'num_digits':
prog.c:8:6: warning: implicit declaration of function 'abs' [-Wimplicit-function-declaration]
    n=abs(n);
      ^~~

Answer 4

Hidden content!
#include   * *   ** **
#include  ** ****  * *    * 
int is_prime(int n)
{
******   ***     ***  divisor;
if (n<=1)
* * * **    *    *  false;
for (divisor     **** ******* *  **   
***   *** * ***   * 
return true;
}
int main(void)
{
** * ****  ** **  **** n;
*  *     ***     ***  *  ** *    **  *  &n);
* * *  **** ** *   * (is_prime(n))    **    * *     *    *******           **   *** *     function return 1
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**   * *** ******  ** ** *  ****  ****    **  *     *   *** ***
*  ** * ****   * **      0;
}

Comments

Case 0: Wrong output
Case 1: Wrong output
Case 2: Wrong output
Case 3: Wrong output

Answer 5

Hidden content!
#include  *   *** * *** 
int num_digits(int n)
{
 ** * ****  * * *  ****    *
**   *  **   ** * ***    ****  **  1;
  *    *** *  ** * **
  ***  **   **  * *   * ***  ** 
 * *     *  ** **  * * * **  ** ** *
}

int main(void)
{
     *  ****   * *  ** n;
* **   * * *     * **    **  ** *  * *  &n);
**  ***  *    *** *** *****     has %d * * *  *  * * ** *** *   
*  *  ***  ** *  * * *  **  0;
}

Comments

prog.c: In function 'num_digits':
prog.c:7:6: warning: implicit declaration of function 'abs' [-Wimplicit-function-declaration]
    n=abs(n);
      ^~~
prog.c:8:16: warning: implicit declaration of function 'log10' [-Wimplicit-function-declaration]
    return (int)log10(n)+1;
                ^~~~~
prog.c:8:16: warning: incompatible implicit declaration of built-in function 'log10'
prog.c:8:16: note: include '<math.h>' or provide a declaration of 'log10'

Answer 6

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
******         * *****  * count=0;
****   * *        ***   ***  ** *   * != 0)
 *  **** ******** *** 
*    ****** * *    **     **** *       ***  ****  *      ****
* *    ** *** * **   ** ***   ****    * *  *  *  * /= 10;
* * ** ** **  ** *   *  ** 
**    * **     ****  * **     ** count;
}

int main(void)
{
* ***** *    **** * *  *** * *   n;
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  * *  *** ** **     * **   * * **   ** * has %d    ********* * ****    
*   * *      ********* * *  *  ** 0;
}

Comments

Case 0: Correct output
Case 1: Correct output
Case 2: Correct output
Case 3: Correct output

Answer 7

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
* * *   *     *    *  *  ** ** ****  cnt=0;
 * * ***** * *  * *   *** * ** **** != 0)
*   * *  *     ** *  ** * 
*    ** ** *       *  ***    * ***** *    *    *    /= 10;
  * *  ******   ** ** *** *     ** ** ** * ** *   **** 
   * * ** * *  ** ******  
* **** * **** ** *** ** *  **  cnt;
** *    ***** ** ***** **  * 

int main(void)
{
* ***** **    ** ** ** *** n;
**   ** *    *  *   *   **** *  *** * **    *  **  &n);
**    *** **  * *****  **  *  *   **** has %d * *****  **** ** * *   ***
 * *    *    **  *   *  ** 0;
}

Comments

Case 0: Correct output
Case 1: Correct output
Case 2: Correct output
Case 3: Correct output

Answer 8

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
*** * ** * * *  * ** *** * *** count=0;
*      ***  ** *   **   *
* * * * *** **** ***  **  * *  *  != 0)
 * ****** * ****   * * * * 
*  ** *  **   *  **   *   **     **** *  ***  *  * **   *
  ** ** * ***** * * *  *  * ***     * * *  ****   *  *    ** ++;
* *    ** * ** * ******   * 
 * ******* * *    ** *** ***  * 
********* **  * *  *  * * ** * count;
}
int main(void)
{
        ** *   *** * * * * * *** * n;
 *  **   * *  ** **** ** ***  *   **   **   **  * **  &n);
**   * ** ******* *   * ****  * ***  * has %d  * ***   *   ****  
 **    * **       * *** ** 0;
}

Comments

Case 0: Correct output
Case 1: Correct output
Case 2: Correct output
Case 3: Correct output

Answer 9

Hidden content!
int num_digits(int n)
{
*** **** * ** *       num_digit=0;/*INSERT YOUR CODE HERE*/
* *     *    **        * **   
 * **  **    ** ** ** * 
**   * *  ***  ** ** ***  *** * * **   ** ** *  
  **** *******  **** * ***   ***  ****   **   *  **** *  * 
  * *  *      ** *** * 

 * *******   *   *****   ** ** *   ** *
* ***     ***  * **  * *   OF YOUR CODE*/
**** ** *   *** * **** num_digit;
}

int main(void)
{
   * ***** * * *** ** n;
*****   ** ** * ******   *  **  *** *       &n);
***** *  * * *      ***  **   *** has %d  *       *    **  ***  
*  ** *   *      * * ** *** 0;
}

Comments

prog.c: In function 'main':
prog.c:18:4: warning: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
    scanf("%d", &n);
    ^~~~~
prog.c:18:4: warning: incompatible implicit declaration of built-in function 'scanf'
prog.c:18:4: note: include '<stdio.h>' or provide a declaration of 'scanf'
prog.c:19:4: warning: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
    printf("%d has %d digit(s)",n,num_digits(n));
    ^~~~~~
prog.c:19:4: warning: incompatible implicit declaration of built-in function 'printf'
prog.c:19:4: note: include '<stdio.h>' or provide a declaration of 'printf'

Answer 10

Hidden content!
int num_digits(int n)
{
** ** ** *  *** *  count=0;/*INSERT YOUR CODE HERE*/
*    * *     ** ***  * **** 
 *  ** * ** *  *  *
 **   * * * * * *  ***** *** * * * *  *  ***  * **  
 ** * *** ***** * *   ** ****** *       **** *** **  **
 *  *  * ****    *

  *   ***     ** **** * * * *****  **  ***
***  * *  * **  * * * *  * ** OF YOUR CODE*/
*      ** *  *****    **  count;
}

int main(void)
{
*** *** * **   **   n;
  *** **  *  ** ***        **   **    *  &n);
** *               ***  *  has %d  ** ****  * *  **     * 
     ******* ** *** ** ** *  0;
}

Comments

prog.c: In function 'main':
prog.c:18:4: warning: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
    scanf("%d", &n);
    ^~~~~
prog.c:18:4: warning: incompatible implicit declaration of built-in function 'scanf'
prog.c:18:4: note: include '<stdio.h>' or provide a declaration of 'scanf'
prog.c:19:4: warning: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
    printf("%d has %d digit(s)",n,num_digits(n));
    ^~~~~~
prog.c:19:4: warning: incompatible implicit declaration of built-in function 'printf'
prog.c:19:4: note: include '<stdio.h>' or provide a declaration of 'printf'