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'