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'