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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* **      * *  ** *  *  **  ***   *   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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* *  ***  * *  * * * **** * 1;
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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)
{
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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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*      *    *******  * * *** * *  ****  * &n);
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* * *         **** * * * *  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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 **  * * ***  ** *** * *
*    *  *    *      ** ***  * 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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** **     * ** ** *  **
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* *   ** *  * ***********  * *** *

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 8

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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* *  **  *  * *  * ** ** ** * ***   ** **** &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'