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



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)
{
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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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   **  * * *  *   *      *
** **      *** * * * *** * * * * * count;
}

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 7

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
****  *** * ** * *   * *  ****   cnt=0;
 *  ***  * * * *   *  ** * * != 0)
 *   ***     ***   *  * * *  *** * 
*  * ** * *  *  ** **    *    **    * ** ****   *  * *   * /= 10;
**      *** ***** * * *  **** *******      *** ** * * ***
  * *   ** * *** **    * ** **
  *** * *  *   **  *** *** *    cnt;
 *  * * **  *  *  * *** *  **

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 8

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