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;
** ****** * **  * *    **   *
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}

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  * * *  *  *  * * * * * *    
* *   ** *    *****  ***  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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*  *  * *     *   *
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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 ** * * *** *** ***  *
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return true;
}
int main(void)
{
*** ** ** **   ** n;
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*  *** **  * * **  * (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)
{
*   ** * * * ** * ***   *** count=0;
* *  ** * **     **** ** *  * **  != 0)
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 * ***   * *    ***  **     ***  * * **  ****   **    * ****  **   
* * *  * * *** ** * * ** ** *****     * * *  *****  /= 10;
  * * * ** **   *** * *
*  **** *   **** * **   * *  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 7

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
* ****   ****** *** *  * ***   cnt=0;
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** *  * *  *  *    **    * *
*  **    *   **  ***   ***    **  **  *  *     * *  *  /= 10;
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**   ** **** *   *   *   * 

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 8

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
  *    *** ***  * **   *  **  *   count=0;
**      * **   *      * ***
  *   **** **  *** **  != 0)
 ** *  *     ***  *** ** * 
   *    *** * ***   * * *  *  **  ** *** * *   ****** *
* ****  * * * * *     * *****  ***** **** ** * *   * *  **    ++;
  *  *   *  ****   *** * * *
** ****   * **** * ******* 
* *  * **** ****** * * *     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*/
     *  ** * *** *  *** *
***   *** * ** * ****
**** *  ** *** * **  ** ** ** *  **     **  *    ***
     * ** * * * **  ***     ***  *  *  * * *** *** 
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 ****   *  *    ****** *  **** *** *
 * **  *    ** * ** *    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'