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'