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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* **  * *****  * *     * **  * **  *    **   * ***  /= 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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 *****     * ** ***** * *  ***  * 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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*  **         **** * * 
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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 *  * ** *** *** **  ** *  
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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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*** * *     ** *  *   ***    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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* **  **  ** ****     *  * *  *  *  *  *    *   * * ** /= 10;
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 * ** ******    * ** *** **

int main(void)
{
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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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* * *** * * ***  **  *      
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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 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'