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

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 3

Hidden content!
#include ** *  *  *** 
#include  **  *  *****  
int num_digits(int n)
{
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}



int main(void)
{
*** * *    **   **** ** * n;
* *  *     ** ***     *** *****     **   *   &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
 * * ** *  ** *   *  * *   * * **  *** *  ***  *    **** 
 * **  *   ** *****         ** *   ** **** **  * *  *    *    *** * ** ***     ** **   * ** * *   *  ***    **   *  * *** *   *****  * *     * **** **   * ****   * 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)
{
* *  ** *  **  * ****   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'