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 ** * ** **   *
#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 **** ****  ****** *   *   *
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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)
{
   *** * **  * *   **  
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*  **  **  *   **  **  
* *      *   ***   *  **
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}

int main(void)
{
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   *  * * *  * *****  **   * 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;
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* * * ****   * *   ****   ** *  ****  * ** **  *** *  * ** /= 10;
***** ***  * ********         
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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 7

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

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 8

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 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'