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'