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'