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;
* ** *** *   *  ** * *   **  * 
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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 2

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

int main(void)
{
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**  *   ** *   ** * * * 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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 **  *** ****  *** ** 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)
{
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if (n<=1)
**** * **  *  *   false;
for (divisor * *  ** ** *    *  * **  **
**** ***** *** * *    *
return true;
}
int main(void)
{
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* * **  *   **  ** * ****   * * **  &n);
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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)
{
*** *****   ******  *   
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*** *  *  *  *** **   **
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}

int main(void)
{
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*  * *** **  ***  * *****  *******  has %d  **   *   *** *   *  ***  
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}

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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 *   ********     *       **    **   ***  **  *** *** **
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*** * **    ****            
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}

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 7

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