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'