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'