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)
{
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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)
{
*  *  * ****      *   ** ** * *** i;
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***      *  ****  * * *    * **
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}

int main(void)
{
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* ** * * *  * **  * *   *  * **  * ** &n);
**** ** ****    *  *   ***  * ***** 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);
 ***   ****   *** **    * *****   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)
{
***** ***   *    * **  * n;
* **   * *  *  * *   ***        ** *  * *** &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;
  *** *  * * *    *
**  ** ** *      * *   *** *
 *  *   * *     * *  *  *** **   *  *
}

int main(void)
{
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**    ** **  *    *****  *  **   *  &n);
* * **       * * ** * **  * ** 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;
 ** ** ***        ** *   *
******* **      * *******   * * ***  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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** **  **  * * * * * ****    cnt;
** *** *    * *   **  **  * ** 

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 8

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