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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* *** *   *   * ***  * **     * 
*** *  *  **   *  *** * *  *   i;
}

int main(void)
{
 ***  ** *   *   *  n;
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      *  *    **  ***   *     * **    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'