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'