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)
{
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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 2

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

int main(void)
{
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   **    *   ***** ****  * *** ** * 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

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#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)
{
*** * *      *********  n;
*** *     ** **   * *    ***   ***   **  &n);
*** **     ** ** *    (is_prime(n))  *    **** **** **  *   *  ** *  *** ***  *  *  * **   function return 1
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*****  ***    * * * **** *   *   *    * **   *      * **** * * **  *    * *** * ****  *  **     *** * *  *** * *    * *    ** *  *   *** *** **  ** **** ** function return 0
   ** *  * * *   *** ** **  * *   * ****   * *  *  ***   *** **   ** *
  *** **** ***  * *    **  * 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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**    **  * * * * *  * *  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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* ***  *   **** *  ****  **    * * ***    ***  *       * **** /= 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)
{
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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)
{
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*** ***  * * *** * *  **  * 
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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*/
**   *** **   **   *  * **   *
****   **   * ***      **
*** *    *  *    ****  *** ** *   ** **  ** * **    
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**       ***  **   *  * *

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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'