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

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 3

Hidden content!
#include    * *  * **** * *
#include **     * *  
int num_digits(int n)
{
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** * ** ****** *    * ***
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}



int main(void)
{
 **  **  ***    *   * * n;
* *    **     *  * **     *  * * *** *  ***  &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
    ** ******** * ***  ** * *  * ********    ***  * * 
*** * * ** * * ** ***     * ***** *  *   * * *  *   ** *   *  ** *  **  *   **********   * * *  * *  *    ****  *    ***    *       * ** *  ****    * *  * * *** function return 0
 **   *   *   *   **   ******  *   *    * **     ****  **  **  *       
 ***** **   ***   ** 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)
{
  * ***      *** ****   *** *  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 7

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
 **  **     *  **  ****     cnt=0;
  * **** ***  * * ** * *  **     != 0)
**** *  ***  * *  *  *  ** 
 **  * *     ****  *** ***** *  * *  **  * *** * /= 10;
**  *  ** **  ** * **   ** ** ***   *    ****    *  *
* *     ** ** *  * ** * **  *  
  ** **  *  **  *   *  ***  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'