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)
{
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** * *** **   * **   **    * * ** ** * **** **
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}

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 3

Hidden content!
#include  ** * ** *** * **
#include  *  **  * **** 
int num_digits(int n)
{
** **  *    *** * *  ** * 
**** *     * **  **   *  *** 1;
* * *  *** ** **  * 
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}



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