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

int main(void)
{
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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 3

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

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)
**  **    *** **** *   *   **  *  ** 
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* * *****       *****   **
* *****      * * * ** * * **** cnt;
   **   ** *   **** *

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 8

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
*   *    * ********* * ** ** **    count=0;
***** *   **     **** *  * 
***    * *   * *     *** **  * != 0)
 *** **    **  ***** ***    * *  
***   * ***      * *** *  * *  *  * ** * ** **   *    **  **
 ***  * ** *** * ** *****  * *** *    **** ***       * * ++;
  * *  * **  ** **** * *
*    *  **** *** ** *****  * 
  *      **      ** *    * *** * * count;
}
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 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'