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'