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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 **  *   *  ***   * *     *
***  **   *****  **   * **       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 2

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
* ** *     *     **     * i;
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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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********* ***   * **   
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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;
* * * * *  **** * *****
  ***  * **    *     *      
   * * *     ******** **    *  *      
}

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)
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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)
 *  **        ***    * *  * 
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 * * ** ** *    *** *****    **       *  *** ** *   ** ** ++;
 * ** **   ***** * *     *** 
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***   * *** **  *     *  *          * 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'