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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}

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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*  * * ***  **  **** **  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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}

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)
{
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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)
{
* **  *  ***  *  * **   *** count=0;
**        * *****  ***    *** *  *** * != 0)
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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 7

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
***   * **  **  *     **      cnt=0;
**  **  **  * * * ****   ** *   != 0)
 *    ***** * ***  * ** ***
** * * ** * * ** ***   *  *  *** ****  *  ***         /= 10;
 ****  *  * *******  **  *  ***   **   *  ****  ****** * **
 *   * ***   *   ** * 
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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 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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** *** *     * * **   * *  *  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 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'