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)
{
          * ***** *   **  *  ** 
* *  * ***   * * * **    *     * ** 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)
{
 ** * *** ** **  * * 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'