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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}

int main(void)
{
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   ****   *  *****  ***  ***** 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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** * ** * * **** * *     1;
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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 ** ****   ***  * ** ***
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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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*  *** *   ** *   *****   *** *  **    * * * &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)
{
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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 7

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

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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**     * ** **   **  * *** 
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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'