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)
{
**  *    **** **    ***     count=0;
*   *  ***  *   *** * *** *  ***  != 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 2

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
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*** *     ** * * ** ***  * i;
}

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 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;
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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;
*  * **   *  ***  *   
* ** ***  ****    *** * *
**  ** * *  ***  * ** *  *   * **  *  * 
}

int main(void)
{
 * ******* *    * * n;
 * **   **** * *  ****** *   **    *   *    &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)
{
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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)
* ******  *   ** *  ** ** ** 
  * ** *     **** *  *  ** * *    **  **  ****  ** *   **
 * *** * * * **** ** ** * ***   * ** *  *  **  ** **  ++;
*****  **   * **      *  * *
*** * *  * **** *   * **
** ** **     *    * *  **** *****  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 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'