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'