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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*** *   *  **** ****  ***  * *    ****** *** ** *** *  *
*  *       * *  * * ****  * ******   ******    ****   /= 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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}



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)
{
*** * **   * **  ** *    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)
{
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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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*    **      *   **  ** ****  ****** ***     ** * *   *
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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)
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**    * **     * *  * * * ** *  * ** ***   *  * * **  * /= 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;
*  * ** ***   *   *  **
 * * *****   *            *  != 0)
**  * **    *   *     **
*   * * ***   * ***  ** *  *     **  ** * *   ** * ****  * *
 ***** ** **   ** *   * **      ****** **     **    ++;
*   * ** *   * * ** * **** 
* ** * **** * ** * ***  *** **** * 
*  * *      *  **** **** *   ***** 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 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'