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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*  ****       ****** *  *   * 
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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 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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***** ** **** * ** * **** *  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)
{
   * ** **   **    **** * **
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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: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;
* *   * ** * **** * *** * * * 
*** ** *  * *  *  *  *** ***  count;
}

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 7

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
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**  **     **  **    ****  
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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 8

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
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*****  *  *  ******* * * 
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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 9

Hidden content!
int num_digits(int n)
{
*****  *** **  * *  *   num_digit=0;/*INSERT YOUR CODE HERE*/
** **  ***** **   ** *  **
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*   *       ** *      **  * *    **  *  *** **** **
 **   ** * ***    *  ** ******     ** **   * ** **   ** 
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 ***      * *  ** * * *  *   OF YOUR CODE*/
 *   *  *    ** ** ***  *  num_digit;
}

int main(void)
{
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 ****  * * *  * * *   * ** ****  ** *  * &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*/
* *  *  ******* *  **  **   *
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* * ****** * * ***** ****  ***  **  **    *  ** ***
**    *   * ** *

** *  ****    ***** *    * * ***  * *    *
    ***** ***   ** **  ** 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'