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'