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)
{
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*** ** * *** * *   ***  
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* ***   ** *** * * **  **
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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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 * ***  * *** * *  *   
**    *  ** * * *   * *   ** ** *  * *
}



int main(void)
{
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 ****** *** * ** * *   * **    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;
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  * **** * * **  *    * *  ** * * 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'