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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**  * *   ***  *   **  *** ***  ** != 0)
* ** *  * * ****   * * * ** *   
**  * *** * *  ** *    * ** *   ******** *     *   *  **  
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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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*  * **     ****  * ** *   ****  *     * &n);
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* ** *  *   * **   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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*  ** *******     **  *** *****      * 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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**    ***  ***   * **  (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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}

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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}

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 7

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