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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* * **** **  * *   
****    *   * ** ** *   *      ***    * *   ****    * *
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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 2

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
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}

int main(void)
{
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* *** * ** **   * **  * * *** 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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}



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)
{
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*     *  **** *** ****  ** (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)
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* *  *** * *      *   * * * * *  ***  * * *   ** **  *     
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  ** ** * ***  * ** **  **
*** ***    **   ** *** * * ** 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;
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*  **** **  **    * ***
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* * *  **  * *  ** *     **  ***   
****    **** *   ****   cnt;
       *  **   ***  *  *** * *   

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 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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}
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'