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'