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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   *  * *** *** * * *     *
*** ** * **      * *** **   ** *  ** 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 *  * * **    *    ***   
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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);
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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       * *      ********
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return true;
}
int main(void)
{
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*    * * *  *** *   ** ***     * *   * ** &n);
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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)
{
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   ***  ** * * *** *  *  ** ***** *  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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*       **   ***** * *  **   ** *****  * *   **   * ** * *** * * 
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****   * * *****    ** *   *
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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 7

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

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**    * * * * **    **    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'