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)
{
  **    *   **  **  *   count=0;
****  **      ** ** *  ** ** *   ** != 0)
** **  ***    *    *  ** 
  * *  ** **       ** * ** ** *   ** *  * * ** * *****  * ** 
*    *** *   ***   *****  *  * * * **    ***  * *   ** *   /= 10;
 *  * ***  *    ** ****  *****
* *  * ****  **   ** *  ****  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 2

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

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 3

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



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
 *   * *   ********* ** ** *****       ** * *           **   ** *
    *   * *** ** **** *   **     *** *   * *     *   *        **   * * *****    *** ** * ***   * * *   * * ** **  ***  **  * *   * *****    *   **  * *   * * * *   * function return 0
 ** * **** ****       * * * *   * ***  *   * ***  *  ***  *  *** *  ****
* *    *  *  ** * *  *   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;
 *  *  ***  * * *  *   ** *  ** ***** *  * * *****  **  &n);
* **** * * *** * *   ** *  *  *** ***  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'