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;
 **  *** *  **  ***     
 *    **  * * *  ****   **    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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***  ** * **  * *    ** ***  *** ** ** ** &n);
*  **     ** *  *   * **   **  * * has %d      * * *   ***   **    *   
*****  * * **** *** ** *    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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* *  * ** ***  * 
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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  *   ** * ***   ****** ** 
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return true;
}
int main(void)
{
* *  *   * **   *    ** n;
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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;
  *** ***    *  * *
   *    * *  **  * ** 
**** ***   *       * ** ***       ***   *  
}

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)
{
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**** **  ** ** **  ***    * * * * * != 0)
*  *  *   * **          **  
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    ** ***** *** *   *****   ******* **   * **       /= 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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* ** **** *  *   **   **   ** ** * *  *  * * &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)
{
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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*/
*    * *    *  *** ** **** ** 
** *****       ** * * * 
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  **  ** **   **  * **     * ***  * *    * ** * * * * *  
*  **** **    *  ***** 

  **   * ****    *  * **  ****    *   ** 
   * ** ***** *   **   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'