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;
* ** **   * ** ** **  **** 
*** * *** * * ****** * *  ** *  *  *  count;
}

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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* *   * * *  **    *** **   ** ** *   *****  &n);
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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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* **   ** ***      *  ** * *   * 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);
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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;
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 ** * **** ********  **  *  * ** * 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)
*   **  * * ** **  *  *** 
  * **  *   ** ***  ***   ***  **  *****  **  ****  *** *  
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  * *  ** * * *  *** *  *******
* *  * * *     ** ** *  ** *  **   count;
}

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 7

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