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

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'