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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*  *   *   ** *   **  **    ** *   i;
}

int main(void)
{
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* *** *   *   *    * *    ***** ******** has %d **  * *  *   **   *** ** 
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}

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)
{
*   *  *       **** ***    *** 
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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)
 * **       *       *   * 
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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 7

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
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***   ***  * **** *****     * * != 0)
  **  ***     *   * ** **  
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*  * ***    *  ***  *  **    * *     ***  ** *  ****  * *  **
**  * *  * * ** ** *  * 
*    *** ***** *** ***   *  * **  * * 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'