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