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)
{
****  * ***  *** **  **   *     * count=0;
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*   ***  **  ***       ** * * 
* * ** *  *  **  ***    ** *  *     ****  **      ** ***
  * *******    ****** ***  *** *** ****  * ** ***** *   /= 10;
**  * * * **  * ***  *** 
 * *  *****     ** * ** * **  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)
{
      *   *  ** **   ** n;
* *  **  ***  ** ** **    *  ****   ***   ** &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)
{
*    **  * **   * ***  n;
*  *   * *       **  ***   * ****** &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;
 **  *   ****  * *** *
 * *    *** *   * *** * **
  *  *   ***** **  * **     * * * 
}

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)
{
  **     *** ****    *   ** **   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)
{
*******    ****   * * *     * cnt=0;
 ** *  **  *  *  * ****   **  * != 0)
**     ***  * **   * *** * 
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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;
 ***   * *** * ***   ** * 
 *****    *** * **** **** *  **** * != 0)
   * *     *  *  *** *    * ** *
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*****   ** *  * * * ***   **
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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'