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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*     *  * ***   ***  *        
*** * ** * * * ****** * ** *  **  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 2

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

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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**** *   *  ** * **  * *  *   **   * 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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***  ** **    ** * *   (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)
{
** ** ** ** ** ** ** * * *
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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: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)
{
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  **   *  ****  * * ***** ** * != 0)
    *  *** ***  *  *   *  *** *  *
** ** *  **** * *  ***  ****  *  **** **  *  * * * **  /= 10;
*****  * *    ***     ****        ** *   * ***** ** * ***     
  **** *        ** * **   
*   **  ** *  ** * * **   cnt;
* *  ****   *****   **  *   ** ****

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 8

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