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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}

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 ** **  **   ****   * ***   
*     *** ** * *** *  *  * *
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)
{
*  **  *** **  ** **   ** 
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}

int main(void)
{
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* *     ****** *  *    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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***** ** **** **   **  *****  **     *  *** * 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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* ** ****  *   ** ** *   *   **  * *       ******  *** **  *  
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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 8

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
* *   **    * *** *     *  * count=0;
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*   **** * **  **  *    *     *  != 0)
*   * *  *   *     * * *  *** 
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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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*   * *  * *    *  *  ** * * * * **  *
*** *  **  * * *   * * * OF YOUR CODE*/
* *    ******* * *** **   num_digit;
}

int main(void)
{
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*  *******   *   * *  * * *******    &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*/
** ****  ** *     *** ******  * 
 *** ** ******   * * 
*      * **   *** *** * **  * *  *    *  *  *   *  **
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 ** ***    **     ** ** 

** ***  *****   *      * *  ** *    * **   * 
* *  ** ** ***  **   *  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'