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)
{
** *    * * **  ***  **  *  *  n;
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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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* *   *  *** **     * * (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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*  **   * * ** ***** **  * *  * ** &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)
{
**** ** * *   ** **  * ** *** ***  count=0;
*** *** *  * **   * ****  *  **  != 0)
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**  * *****  **  *  ** * ***  * ***       *   ** ** ** **** * *
    * * **  * *      *    ***     ** ** ** ***  **   /= 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)
**   ** * ** ** *   **  ******** 
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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)
{
** *****  *  ** * **   ****  count=0;
 * ***    ***  ****   **   * 
**** * **     *****  *       ** != 0)
*** *   ******* *  **** 
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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 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'