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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*** *  ** *  *****  ** **  *
*  **  *   ***   * * **  ** ****  *  * ** * ** **** *  ******* 
*    **** *  *     ** ***** *  * *  *** * **   * /= 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 2

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

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

int main(void)
{
* *    *   ** **   ** * n;
**  *   * *****  *** * * ******  &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)
{
 *  *  **** *     *  *     n;
*    * * ** * ** * **    *  * **  **  *  ** ***** * &n);
 ** * * *  ***          * *  **   ***   * 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)
{
* *  ** ** *  ***   ****  cnt=0;
  * ***   *   ** * *   *  **  *** != 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;
*     *** ** *** * *  ****** ****       *        * * &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'