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)
* ** * * * ***** *** **  ***
   * ** *  * *   ***   * **    *  *     ******  * * *  * ****   ** 
  *  ***** *  * * **   **** *    *     * *****     ****   ***  /= 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)
{
*****  ** * **   ** ***    *    i;
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**     *****    ** * *  ** * i;
}

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 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)
{
   * ****** ** *     n;
  *         **  * *  ** ** **   ****   &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;
*****  ** * *   * 
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    *     *******   **  * *  * *   
}

int main(void)
{
*     ** * **** *   * ** n;
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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)
{
**  * **  *     **    **** ***  ** count=0;
*****      *    *   ***  * * ** * != 0)
   * * *  ** * *   * **** * * *
* *** * *  * *****   *** ** ** *   **   *  **** * *  
*  * *    *       **** **   ***** **  **  ***   *  *  /= 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 7

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