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'