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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** *****  * * ******* *    ** ***  &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)
{
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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
* *   ** **  *  *** * * *  * *   **  **  * * * *   **** ***
*** ***  *  ****    * ** *   *   * *   ***** *** *  *  **   * ** **** ** *      *    *       **  ** **** *****  *  ** ** **** ** **  **    * ***** * ******* * 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)
{
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*   *  ***   *   *       * * ***     != 0)
*    * ** *   ****    *** ** 
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***** ** ** *  * *       * ** *  ***  * * ** *     ** * /= 10;
*      **  * * ** * *  ** *
**** **** **  **    *   ** * **  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)
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*      *      * *     *     * *****      ****  *    /= 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'