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'