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)
{
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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 2

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
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}

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)
{
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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)
{
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**     ***** * *** ** **       *  *   * ***  &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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*   ***    ** *** * ** **** *   **   *  *  ** * ***    /= 10;
  *  ***    **  **  **  
* ** * *  * ***  **   **   ** ** count;
}

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 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;
      * ** ***  *  *   *  * 
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*  *****  *  * **** *********
*   ***  ********* **  * **  * *   * ***  **** *  * *  * * ******
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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 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'