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

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

int main(void)
{
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***  *****    ********   * 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 *  * **    * * ** ***   *    
***     **    * * *  *   *
return true;
}
int main(void)
{
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*   **** *   **  *** *    **  **  &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)
{
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* * **      ***** ** * **   ** * * &n);
**  *** * * * *  ***      *  * 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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** **** * ******   **** * ** 
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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 7

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

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