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)
{
**** * *  * *  ** ** *  *   count=0;
  *  ** ********** **  * * **     != 0)
  * ***  ***** *  *   *   
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****   *  * *   * *** *  ****  **  ********   **** * /= 10;
   ** ****    *      * * *  
  * *  *** *   ***   * * * *  *  count;
}

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 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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***    **  **  *** 
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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;
*   *  * ** ****** *** 
* *  **   *****    ** 
**    * *** * *        *  *      **  
}

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

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
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** ***  ***** ** **   *  *  *  != 0)
   * * ** *  **  **   ** 
**  ****  ***  **  ** ****    ** *  *   *  **    *   /= 10;
**   *  *           * *   *   * **  ** *    * *  * ***  **
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**   *   * **  **  *  ***  **** ** cnt;
* * * * ** *  **    **  *  *

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;
  * ***  * *****  * ** 
**   *   * ** *** **** **      != 0)
  **   *  *** * **   ** * ** 
 *  **   ** **  *   * **      *** ** *   * * * **   **** ** 
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* **  * * *   * * **  * *  
*  ***** **  *** * *  *   
*   ***** ******       * **   * count;
}
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 9

Hidden content!
int num_digits(int n)
{
 ** *  ** ***  *  num_digit=0;/*INSERT YOUR CODE HERE*/
*   *  **   ** **    ** *** 
 *****   *  * * **** 
 **      * **   ** ***  **  **** ** *  ** *   ****** *   
   * *   *     * *** ** * **  ** ** *** * *   **  *** ** 
** *   ****        **

**    ****  **  *** * ** * ***    *     *
**   ** * **   *     ** 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'