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)
{
   ** *  ***  * * **  * * count=0;
  * * ***    * *    **   *   *    **  != 0)
 *   *  * *  * ***  *   *  * 
 **   ** ** ** *** * ** * * *   *  *     * ** *  ***  *  *  *  *
**     ***     ***     *** * *  * * **      ** ** **   *  ***  /= 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   ***   **** **   *    ***
 * *  *** ****  *   *** *
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;
*** ** *  *** * *
* * *     *  ***   *  * *
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}

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)
* *** * **     ***********
   *** **** * * *  **  **  **   **** **   ** **  **    *   **   
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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 7

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
  **  *  * *  *** * * **   **     cnt=0;
   * **** * *  *  * * **    *   != 0)
** ***  * ** ********   ** 
*  **** *  * *   * * ** * *   **  * *  *** *   *    *    /= 10;
  *  *** * * **  * *   * ***  * *****  ** **   * **   
*  **  **  *     ** *   * ***** 
** *   * * ****  *** *** **   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;
*  ** *  * * *  ** * *
 ***  ** *** ** ** ***  **   *  != 0)
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*       *   **   *  ** *  * * ** *  *    * * ***    * *    *   **  **
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******* *** * *  ** *    ** *  * 
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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 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'