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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*  **    ** ***  *  ****  * ** ****  1;
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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;
**       ****** *** * 
 *   *  *** ** **  ** ****  **
**** * *** **      *  *  **** * **
}

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)
{
** * * **   * ** **  * ** * *  cnt=0;
***   *     *  ***** ***  *   != 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;
***    ** **  *     *      
  * ****** *  ** **   **    *  *** != 0)
 *  ** *  * **  *    *** * * *** **
*  ******* * ***     ***** ** *     * **  **** ***   * * ***  *
**    * *** **  ****  ****     * ** **** ** ** ***    ++;
**    *** ** **  *** **
*****  * * ** **  *  **  * *
****       * *  **        ** 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 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'