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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}

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