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;
*****    * * ***** *****         ******** *  *
*  * *** * *  * ** **     
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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)
{
* *** * **  *     * *  ** *
*  * **  ** ** *** ***** *  * *** 1;
     *  ** **  *  *    
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****  **   ** ****  **     *  ** * *   
}



int main(void)
{
   ** * *  * *  *  ** * n;
   **    ** *      * * ****  **  * *    *  &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;
 * **       ** *  *
*  ** ** *  ** * * * **   * **
**  ******  *  ****  * * * * * 
}

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)
*  **   ** ** ******* *   * *
* * *** *    *   * *   *  *  * ****   *** * *     *  *   * * ** 
** *   *  ** ***   ** *   *****  *** **  *  * *  * ++;
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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'