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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** *  ***** * *  **  ***  *       *   &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 3

Hidden content!
#include    * * *     
#include **  *  *   *   
int num_digits(int n)
{
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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 *** *  * **     * * *****  *
      ***   * *** **     *  *  
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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*  *  ****  * ****     * ** **  * * **    &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)
{
    *      ****** ** ***   *** count=0;
*   *** *   ** ** ** *    ****   != 0)
**  *  ***  *  *  **   ***  
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* ******  **       * * * *** ******   *    ***    * ** /= 10;
  *     *   *  ****** *   *   **
 ** ****  **    * * ***  *   * count;
}

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)
* *   ** * *    * **** ** **
* ****  ** * *** ***  **   **** **       * *     * /= 10;
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  ** ******    * *  ****** 
 **  **** ** *** ** *** **  ***  cnt;
*** ******    ** ****  * *

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 8

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