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)
{
 *  * ***** **  ***** *** *  i;
 *  **      **  * ** *     * *   * * * ***
 *   ** ** *  * **   * *  *
** *    **   * *  *** **** ***  ** *  * ***  **   *      **  
* **** *** ** ******    ** ** * **
**** ** ***  ** * ** *  **  **** i;
}

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 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
 *** *   * *   * ***  * **     ***** ** **       *** ***** **
**********  * *   *  *    ** *    ******            ** * **** *** **    *** *  *  * **** *     *     ** *  ** *** *** * * * *        *  *    *    ******  ** 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'