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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* *** **  *** * *  * * * **   * 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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*  **  * * ***   * *****  **  ***  ** &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  *** *** ***      *  *   * **
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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)
{
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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;
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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 7

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