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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  ****** * **  *** ****  * *
    * * *    **    * *** * * 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 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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}



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)
{
 *  ***** **  *           
*    *   **   * *   ***   *  * 1;
   *  * * ** * *  *  **
**  * * *  * *    ** * **  * *
*  ***  ** *  ** *      ** * ******
}

int main(void)
{
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***  * * *  **  * * **   * ** * *** ***  * &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)
{
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  * ** *** ** **  **  * **  != 0)
****  ****** * ****  *** * * * *
    *   *** * *** * * ** *   *** ***    ***   *  *** **  *
*** *  ** **    * * *       **** ** ** *********    /= 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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* ** *** ******  *   *** * ** * != 0)
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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)
{
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* * *   * *   ** *******
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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)
{
*    *** *   * *    ** 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'