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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  * *  **    *****     *  ** *  **  ***   *      * ***  /= 10;
     *  ***  **   ** ***  *  **
****  *****   **** *    * ** * count;
}

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 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)
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for (divisor  ****  *    **** * * *    **
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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)
{
* **  *   ** * *  * n;
* * *   *  * * *** * *  *** * *      &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)
{
 **   *  *    * ** * ** ***    * count=0;
* * **  ** ** **       ** ** * != 0)
*  **     ***  **  * ***    *
***  *  ***   * ** ** * * ***      * ***  ** * *** * ** *  ********
* *    * *** *  * *   *** *** **   * ** *****  **       /= 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)
{
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* *      **** ****      **   * * * != 0)
* ** ** ** *  * **** *     
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* **  * * *     **    **** 
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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)
{
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***  **  ***      *  *
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  **   ** * * * ** *  **
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****  ***  *    * ***       * *  **  ***** **  **   **  ***** * ++;
***  *  * ** * ****  * * * *
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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'