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  ** ** * * * *    ****
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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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*    * ** ****   **  ** * 
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}



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

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)
{
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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)
***   *   *   * *     **  *
* * ** *  * *        *     ** *  *          *    *** ** *
**   *****     * **** * ** *  **    ** *     **** ****** **   /= 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 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;
* ***  *****  *    *** **   *   * ** *  * * ** &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'