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)
{
*  **  * *  *   *  ** * *   i;
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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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** ***         * * 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)
{
**  * **  ** **       *  * *
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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)
{
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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 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)
{
* ** ***** *  ** *** *   n;
* * **  * ***** *****   **  *  **   *** ** * &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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* **  *  **        **** * 
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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*/
 ***  *    *   **    *** *   
****   ** ****   *  * 
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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'