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'