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;
  *   ***** **    ***     *** * ** ***   * *
*** *****   *   *  ** *  * **   
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* * *   **   *   *    * ***  
   * *  * ** ***  **** *  *    * 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)
{
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 * ****  *  ** **  *** * ******* 1;
*  *     **** * *** 
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*  **  *****  *** ***   *   * *    
}



int main(void)
{
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 ** ** ***   * ** * ***     ** *  * ** &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'