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)
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****  **** * ** *********   * *  *    **  *** *** * ** 
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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 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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*   *  **** ** *    *   * * 1;
** ***     ***  * * *
** * *  * **** ** * * 
***** ** *  * ** **  *      *
}



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)
{
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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)
* **    *  ***** ***  **    ****
* * ** **  *   * *  *  ** ****      ****** * * * **  
 *   ***   *  **  * ** * *   * *      **      **   *  /= 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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 ****    **  *  ****   * 
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* **  * ** *   * **    ***  *    count;
}
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 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'