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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**** ******   ** ***     * **  **  has %d ***  ** * * * **  *      
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}

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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}



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;
* ** ****   *  *  
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}

int main(void)
{
**  * *  ** **   *   **  n;
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*   * **  * *    **      * **  * * * * * 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)
{
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**   ** ***** ** ****  * * * *      != 0)
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  ****** * **** * *  ** * *** *     *    **  *  ****   *
*     *  *   * **                **  ** **** * * * * * * ** /= 10;
  ***  *  ****    *  *    
** ****  **** * * * * *  ****  count;
}

int main(void)
{
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 **  *****    *   *    *   ** *  ** ****     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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   * * **  * *  *  ***  *   ****   *  * ***  *   * ** * ***
  ** ***  **  *   *      **  
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* * *     **  **  * ** * 

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;
  **  **** **   *** **  *  *
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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 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'