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)
{
*  * * ***   *** ***  **   
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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)
     * * *  **** *   * ****
    *   *  * *  *   **   * **** *   * * **   *  *  **  ***
 ** **  **  ***    * *  *   * *** *   * ** *     ** *     *** ++;
     ** **  ****  * *  * **
 ***   ***  * *****   **
***  * ***   *  **** ** *** ** *   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'