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'