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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*  *        **  *  *  ** *   *** *   *  * 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 * *   ****  *  *
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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)
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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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}

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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}

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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***   **   **  * **** *** ** ***    **   **  ***     *** /= 10;
 ***   ****** **  ** **  *
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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)
{
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* * ******   * * ***** ** * != 0)
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*   *  * **  * ** *  * ***  ****   * cnt;
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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)
{
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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*/
**    **    ** ****  ** 
* *    ** *  ***  * * *  *
****     * **  *  ****   **   **** *    *** * * *  ***  *
**** * **** *  **   *    ** *        *** ** *** **   **  **
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* * *    **     * ** ** ** * * 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'