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'