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)
{
  **  *   *** *** *   *** **     i;
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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)
{
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**  * **** **   ***** **
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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)
  **** ** ****   *     *  * ** 
*** *   ***** *  * **  *   * ** **      *   *   ** ***  
*******  * ***    **   *  * * * ******  *  *  * ** ***  /= 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)
*** *     ** *****   **  *
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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'