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



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)
{
**   *  **  * ***   ** divisor;
if (n<=1)
 *   * *  * *******   false;
for (divisor  *    * *** ** * **  *** *
***  ********        **
return true;
}
int main(void)
{
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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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*** *   ** *  *** * **    ** ***      *      *****  ** *  **
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** **   * * *****    * * *   
* ** * * * * *****     ***** ** 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)
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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 8

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)
{
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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'