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



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)
{
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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)
{
** * ***     *  ***  *   *  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'