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;
  ** * ***   **  *  **
** ****   *  *  ** ****  *
*  **  *   * **   * ** * *  *  *****
}



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)
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*** *     *    * **   * *     * ** * *    *****   ** * /= 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)
{
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**  ** * *    ****  * ** *  *******   * * *  &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'