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)
{
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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 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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** ** *   *   * * ** * **     **** * &n);
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* * *  ** * **  * * *  * 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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*** **  * *   ***  **  **  *  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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***** * **  *  * *  * *  **    *
** **** ***   *  **  * ** ***     * count;
}

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 7

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