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'