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

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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*  *****   * *  ** ***    * *
* *  ** *  ***  *   ***  ****      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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***   * ***  **** * *** * 
****      ***   * *  ******* * *  **   != 0)
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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)
{
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  *      *** * **  ** *         * ** *  &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'