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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* *  *   ****  **   *   * * * != 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 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)
{
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** * ** **  * **  ****   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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*   *  **  ****  * *****  **  ******   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)
{
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  ******* **   * * *** *** ** * != 0)
** ********       **  *  * *  
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* *     ***  ***    * **** *  *** ****     * **** **** **    /= 10;
 *   *    *   ** ** ** **** 
  **   ********       **  * **  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)
{
 *  *   *  * * *    *** cnt=0;
 *** ** *** * *** **   *  ** *** != 0)
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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;
 *    ** * *******  *  **  
*    **** *** ***** * ***  * *** != 0)
* ***  * **   **   *     * * *
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 *   **   * * *  * ** * 
** ** ** * ****   *  *  
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}
int main(void)
{
** * *    ** **  *  ** *      n;
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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 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'