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)
***    *  *  *  *    *** 
***  ** * *******  *  ***    ** ** * **   *** * **   ** *
*  *   ** * ****  *  * * *  **  * **   *******  *  **  * /= 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 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)
{
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* *** * *   ***   *  (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)
{
*** **  * ***  *** *** ***      count=0;
*      ****** *  ** * **  != 0)
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* *  **  ** *  * *  ****    *  ** *   *    *  **  ***  * 
*  ****  *      * * **   *** ** *    * *    * ** ***     /= 10;
  **  ** *   ***    *** * *
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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 7

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
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****     **     * ** ** *    *  **  **   * ** *  **  *** /= 10;
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****** *   * ****       *    *
*   * *** *     *** * *      cnt;
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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 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'