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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 * *** * * *    ***   ****  
*** **  * ****  *  * *  * **  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);
 * *****  *  *  * *   *****    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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  ** * * *  * * * *  *  ** **** *       *  &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)
 *     *   ***  ** *  * *  **
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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)
{
* ** * ***   *    * *  ** ***   *  cnt=0;
* ***  ***  *   *  * * * ** != 0)
*****    *     * **  ****  ***
****  * *     * ***** *    ****  *   * **       **** ** **  /= 10;
 ***  *      *    ****   * **** ** ****    * *  **  * * *
*  **  * **** * ** ***** *  * 
 ****** *    **  * *    * *  *     *  *  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)
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****  ** *  *** ****     *   * **   **   *    *  ***   
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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 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'