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'