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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    *    *** *** ***   **   ** 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 2

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

int main(void)
{
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** ****   * * *  *  ***  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 * **** *    **      * ** *   
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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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* ***  *  *     ****  1;
** *  *      ** ***   * *
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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;
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***  **   ***   *   **** *  * *  * count;
}

int main(void)
{
*** *   * **   ****** *     *  n;
***  **** *  **    * ***  * *     **  *  *  *** &n);
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**  ***  ** ***  *** * * * *  * 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;
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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'