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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 **** ** * *            ***   * *   *  ** *    *  *  * ** *  /= 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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*****  *** *  ****  ** * ** i;
}

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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}



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{
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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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*  ***** ****   *****   ** *   * *   **    &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   *****  * ***** *  ** * *
* **   ** * ** * **  *   *** 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)
*     ***    * *     * ****
*** *     **    *  * ***  * **   * *  * ** * ** *** *** ***    **
* *      *    * *** *   **  *  ******* ** ***   ****  **** /= 10;
*    *** * * *****  * ** *
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}

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;
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**** *  *** *  ***   *  
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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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}
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'