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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}

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

int main(void)
{
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*   *  *    * * **  *  ****** *  **   &n);
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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)
{
*   ***  ***** *   * *** **     * count=0;
*    **  * *  *  ****  **  **     != 0)
 * *   ***** *** **  ** **  *** 
*      **           ******   **  **  **  * * *       *
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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 7

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
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* *** ***** ** *  *** * *  ** **    != 0)
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   **  **  *   ***  * **     *****    **  **  *      ****  
*  *  ** *** * * *   ** * 
**      **  *  *****   ** *    *  *  cnt;
  * * **  ** **  * **  * ** 

int main(void)
{
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**   *** ** * * ****    *** ** *** *      * &n);
* * **** *  ** ** ** * ***     * *   has %d * ** *****     *     * * 
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}

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;
 *  **   ** * *** **  *    
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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*/
* * *  ******* * * *      
*   ** *  * *  ****
*** **** *  **  ***  *  **   *   * * ****         *
**  *    * **  * ***  **** ****     ******  *     * *  * * *   * 
 **    * ** * ***       ***

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