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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* *        *    *      *** ** ** i;
}

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 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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** *  ***   * *    **  *        **  * *    * ***  **  * **** * *  ***** ** * ** *** *  *   *  ***   ***   *   * * * *  * *** *  *** *** *  *    **   *   **  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)
{
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 * *   **  * * ** **   * **      ** *   * * &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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*  ** * * * * ********  *  ******      * *  *** * ** /= 10;
*** **    * *   *  *** *  **  *  * * *  ****  * ** 
 ** ** *   **** ***  *** *
   * ** ***  **** *  * *  ** * ** 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;
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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 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'