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)
{
* * ** *  ***  *   *** * *  * count=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 2

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