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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** *  *  ****        *** ** ****    **   * ***    *   **   **    
       * * **** *    ** * *  **   *  *     * **** **   /= 10;
**   ** * *******  *   *** **
  * *** * *** * ****  *    * * *** 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 2

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 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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**   **   * * ** * * *   ***  *  *    &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;
* *  *** **   ** * *
**  *  **    * ** ** *   **
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}

int main(void)
{
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   * *  * **   *   ** ****  *** *  has %d   **   * ****** *  ** 
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}

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)
**** * *    * **** *  *** ***
** ** ** * *    ***  *  * *  *    *   *  ** ****      *
*** ****  ** * *   ** * **   *  * *** * *  ** * ** ***  /= 10;
*****  **** ** *          **
   ** * *  * **      *  ****  * *   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)
*  ***     ** * *    ** ******
 * *   *  * * * ** *  * **   **  * ***   ***    * * *** /= 10;
******   ** * ** **  * **  ** ****  *    * * * * * ****    
   * *         * **  ** * *** 
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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;
*   *** *** *       ***   
*  *****   *   *    *   ** * != 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 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'