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;
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}

int main(void)
{
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* ***  *****  *  **  ** *   *  * ** &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)
{
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*****   ***  * **  * **
**    ** *  *** ** * ** *  *** * 
}



int main(void)
{
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 ** ** **  *  *  * ***          *** ****   &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)
{
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  *  ****        * **  *     **  **** ** &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'