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;
***  *******  ***   *** *  **** * **  != 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)
{
*   ** *** ** **    * * * ****   i;
***  *  *** ** *   *  **   * ***  * ***  *  * *
* **** *  ****  ** * * ***
* *** **     * *   * * *   ******    *   *    * *   *  
**  *** ****   *  ****  *
***** * * **   ** * *  **   ** **   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)
{
 **   *   *   ** * *    ***
  **   *  ****      *   *      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: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;
*  **  *   ** ** *  
*  ***   *  ** *** 
***    **   **     * *** *     * ***  
}

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)
* ** ** * ** *  ***   *   **  
*  *** **** * * ** * * *     ** *** ***** * *  *    ******  *    
 **   *****  * ******  * *  **  * **    ****  *   **   *** /= 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)
*   ** ** ***  * * *     ** 
  * **   * *     ** ****   **  ***  *  * *  *  ***  ***    *
**  ************ ** * ***  * *  **   **  ***  **    *** * ++;
**  **    ******* ** ***   
* **  ** *  *     * * ****   
* ** ** * ****** ** *       ** 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'