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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* *   *  *** *     *  *  * 
*  ** **     ****   **    ** **  * * *  ***  * ******   
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*  **   *           *** * ***
*** *  * ** ***   **** * *******  ** 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 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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}



int main(void)
{
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*      *  ****  * *   * * ** *   *   *  ** &n);
* ****** ** ******   ** ***  *****  has %d     **   ***** *    * 
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}

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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  ** *  * ** *    **   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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*   *  * ****  * *             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)
{
**          *  *** *  * * * *  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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int main(void)
{
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** ** *  **     *  *** **** **      * * &n);
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 **** *       *** *   ** 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)
{
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** ** *  *** * *  * * * *  != 0)
*    * *  * ** *  * *   * *
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****  *   **    *     **  *** 
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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 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'