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;
*  *   ****  ** ****  ** ****   ** * ***** ** **
*  **  ****  *** *        
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** * *         * ** * *
***** ** * * **  *  ** ** **  * 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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** * *   * *  *   *   **** *    1;
** ** * ** **  * **
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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'