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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     ** *       *    *** **    != 0)
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**  **** *   *     * *  * **   * **   ** *       ** * **  * /= 10;
* **** *****  ** * * * *  ** 
    **    *  * **    ** * * *      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 **  **    *** *** **  **
** *  ***  *****     *       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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    *  * **   ****    ** *     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 **** * * *  *  **  ****
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return true;
}
int main(void)
{
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*  **    **  *   ** *****  *  * *   **  * &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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* * *   *   **** ***** 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)
{
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**  * * * ** ** * *  * * *** * != 0)
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****             *     ******  ** **    * *   **** /= 10;
**   ***   ******* * ***   *** *
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}

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 7

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