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)
{
 *   *   *     * ** * **   i;
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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;
   **  ***   *
*** ** * * * **  ** ** *  
 ** ** *   ** * ** *   ***     * ** * **   
}

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)
{
* *  ** * *****   *  **  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)
*      * *********** *  **
  * ** *** ****   ** * ** **** * **********  *** *   * /= 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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     *** * * *  ** *  *  * *
***   * *    * *  * *** ****  
 * *   **  **  * *  * *  *  ***  *** * 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'