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)
{
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*** *  * *   *****  * *   *   ** != 0)
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  **   * *** * * * **  *  * ***** *  * **  *   **   *   * ******* *
*  *   **   ** *** ** *** ** * *   * * * ** ** **  ** /= 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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}

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



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
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*  *  *    * ** **   *             ****      * * * *   *  *    ** *** * * ** * ** * *    * * *  **  **    **   * * *   ***   **  **   *   *   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)
{
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 * ***** *  * *   * *     * ****   *  != 0)
  * ****     *  * *** *  * *
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  ** **  *** **  * **  ***   *  ** * *       * *  * * * * *
***** * * **  * *** *** * ** 
  ***  * **** *        *   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)
  *  **  ***    *  *       
*  *  ***** ***  **  *** ***  **  ***    ****   ** **** 
*    **    * *  ** ** *  *  ** **  *** * *    * *** * * ++;
 *   * * *** * **  *  ** * *  **
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* ** *  * * * ** ** *   *   ** 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'