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 *   *     * * **** * *
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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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    ** * **  *   * * * *      * 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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 **** *      *  *  * (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 **   ***  ** *   * *** *
*  ** ** *   **      * 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;
* *  *  *  * * *** *** * ***
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}

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 7

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
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   * **     ****  * *   **  != 0)
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*   * ***  * ** *  *   * * * **** *   * **   * **  *****  
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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;
    *  * * *  ** * * *
*   ** *  * * *  * * * * * ** * != 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 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'