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)
{
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* **     *** ****         **   * *   * **  *    *  
***** * *  * * * * *    * ** **
**  * * *****     **   * ** *  **   * * *   **  * **  *  *     
** *   *** *  **    *  
***  **  *****           **     i;
}

int main(void)
{
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 ** * ** *****  **  * * *   *** *  *  &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;
***   *  ******* ** * *
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}



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'