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'