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)
***      *  ** **   **
* *   ** * ***   **  *   *****   *   *    * *  * * *   ** ** 
*  **  * *  **   ***  * * *  ***  *****   ** **** ***  /= 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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*  * **  * * * * ** ** ** * 
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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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**       **  ****  ** ***     * **** ***** &n);
*** * ** * **  *   *   **** ****   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)
{
** * **    *       *  **
** *   * * ** * *  **  *   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)
{
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****    ****   ******   ***   != 0)
* **  ****  * * *  *** * 
** * *** ** *****     **  ** *** ** *    ** *   * *****    *   *
*****  * * ** ** **      * * *  *   ***** *  ** **  ***  /= 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;
     ** *    *** * * ***   ****     * *  ** *   * *   * * 
 *      *   ****   * *  *  
 **  * ***  ***   *** * *** *  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)
{
* *  *    * *  * **  *   **  count=0;
 * * ****  ** ****** ** 
**  *  ** ** *    **  * *    * * != 0)
*  *    ***** *** * *   ****  
 * *  * * *** *  *** **     ****  **   *** * *  *    **
* * *****  ** * **     ** * *   ** *** ***    *  * *   ** ++;
 ** * * ** *    * *  ** **
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** ****  **  **     * * * *  ** ***  count;
}
int main(void)
{
*  *  ***** ** *   *  * ** n;
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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'