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;
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***  * *   * * * *** **    *  * 
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** *****  *   **  *   **    **     *   *    *   *  ***** /= 10;
 ** **   ***  **    ** 
* **     * * ***  ***  *  * *** * * 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 2

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
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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)
{
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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   *** * *   ** * **    **
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return true;
}
int main(void)
{
  *  * * ** ***   * n;
** ****** ***** ***  ****    ******** **   &n);
***  ** * * * *  ***  (is_prime(n)) **  *  *   **  *  *   **      *  **   **** *   **  ** *  * function return 1
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  * * ** ****     * **  * *** * *** * *    ** **     *    *   
*  *   *   * **   **** 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;
* *  *       ***** * **
**   ***  ** ** *  **   *
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}

int main(void)
{
* *** * * ** *  **   **  * n;
* **  *  * *** *** ** *   *   *  *     *  &n);
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* ** ** *  **  * ****    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)
*****   **   * *** * *  ** 
**** * * *   ** * *    ***  *****    * * *    ***** * *  *  
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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 7

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
**** *****  ***** *  *  *** cnt=0;
  *** *  *   ***   ** *** ***  * * != 0)
* *  * * ** * *     *  *** 
* * *******    *  * ** * * **   ** ***    **   * /= 10;
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*    * **  ** *  ******  *  *** cnt;
   *  **    * ** **  *** **

int main(void)
{
** ** *   ** *   ***   n;
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***** * * * *   ***     **  * **  *  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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 * *    * *** * ** * ** * ***
* * *** **  ** * ****    ** 
**  ** *** ****  *    *** 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*/
***   *  **  * ** ** ***
* ** **  ***** *  ***
 *    * * ***  **** ***  *   * *  *    **  * *** **
   ******** ** * *         ** * *  **   *   *** ** ** * * 
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      **      *       * * *  *  * *** *     * 
*** *** * * * *   *    *  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'