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)
{
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*       *  *** *    *      *  * * ** *  ***  *****  ***     
***** **  **  **  **  ** *      * **  *  * *  *  * *  *   /= 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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**    **   *********  ***  ***  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;
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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  ** *** * * * *  *  ** *  
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return true;
}
int main(void)
{
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**** *  **    ** *   * **  *   *   *   ** &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)
{
*   ** * * *  ** * *  n;
** *   *  * *  * *** * **    *   * **         ** &n);
*  *  *   **      **     *   * has %d *    ****** *    *** ***  
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}

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)
{
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* *****  **    *   ** *    * ********* 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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* ***  * **  *** *** ** *     ** * ** *   ***** **   /= 10;
**   ** ****  *  **    *   *    *  * * * *******    * ** *
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**   **  * *  **   ***  ***  cnt;
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int main(void)
{
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** *** **   * * **   * ***** *   *** *    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;
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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 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'