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)
{
****   ** *** *  ****  **  ** ***  * n;
 **** ** *     * *    **       **   *  ***   ** ** &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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 **** *         *  *** **  ***   i;
}

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 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
****   *   * ** *  ***   *  * ** ***   ****   *****  * * *   **
*** *  *         *  ** ***** *   **  * *    *  *** *  * *  ** * ** *  *   ** * *   *** *   ******* *  * **  **  *** * * *   ***   ** *** **          function return 0
 *   ***   * ** * * **  ****** *    ***** * *    *          *  *  * *** **    
  **  *    *   * **     * *   * 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)
{
**  *  * *    **  * n;
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    *** **  ***    *  **  *   * 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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*    *****         ** * ** *** *********  *** &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)
 * * * ******   *  **  *   
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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)
{
* ** **    ***   **  *** *   count=0;
** * **** * ***** * * *** * ** *
  ****   **  *   * ** **   ** ** != 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'