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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**  *   ***    ** *  *         *   * *   **  * *   *****
*  ** **  *   ** *** **   *    *   *  **** ** **** **  **  /= 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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}

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)
{
**   *   * * ** * ** *** 
**   ********     * * **    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
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*  * *   ** *** *  ** ********  *** *** *** ** ** *   * ***      * ***  
    * **    * *  *  ** * *  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)
* * *  *   ***   * **  **** 
 * *  ** *  * **  *   *  ***    ** * *****  *  ** **     
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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 7

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
  **** *** ***  * *  ******   cnt=0;
    *  *    *** *** **** *  *** * *  != 0)
   *    * **    **  **    *** 
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  ***  *    *****  ** **  * * ***   **  ***** *  * **
       *  * *     *** ** ** 
* **     * *    * * * **     cnt;
 ***   *  *  * * * * *  

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 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'