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)
{
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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 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 *   * * *   * *** *   
** * *** *   ****   * ** 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)
{
* * * *  * **** **** * * n;
**  **** ** **      *  ****  ******* &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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** * **  *      ***    ***  ** *****    *** ** &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)
  **** *      * * ** *  **
***  * * **  * **   *   **   ** *   * **  ****  ** ** **  *  
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 * *** * **  * *  ** * **     *** **
     ** *  ******  *  *   *******      count;
}

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 7

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

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 8

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