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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**** *** **      *   ***  **  != 0)
*  ****** * **  *    *  *** 
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***   *  ***      *  *  *    *  *     * ***** * *   * *** /= 10;
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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 2

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
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}

int main(void)
{
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*    * ***** **   *  *  *    has %d ****  ***  ***** ***** ** 
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}

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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*** ** * * **   *** 
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}



int main(void)
{
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***          ***  ** **    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)
{
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***   * * * *    * *  (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)
{
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*** ** ***    **  ***** ***  *    *    has %d     **   *  * *   ** * 
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}

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)
{
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****** *      **  * * *  ** *      != 0)
**** * * ****   *   ** ** *  
* *  *   **   **  ** ** **    **    * *   *  **  
***  **  ** **   *** *  ** * ** **  * ** *** ***** /= 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 7

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
*** *  * *     *  ** *      **  **  * cnt=0;
* *  * * * ****  *  *    *    *** != 0)
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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 8

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