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)
{
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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);
*  *   * *    * ****   * ******** ** 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)
{
** *  *       ****** 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)
** * * ** * *   *      * *  **
* * ****     ***   *      **  *  *  ******   ****** ****** * 
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****  ** *  *    *   **** * 
 *   * ** *** ****  **   **  * *   * ** count;
}

int main(void)
{
 * ******   *   *** *  **  n;
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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 7

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

int main(void)
{
*     **     *  *       *    n;
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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 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'