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)
*    * *  * ***** *  *   **
**   ** * ****  * *  *  * ****   **  * **  *** * *
* * * **** * *******  * *  ** *** * ** * * *** **  * ***  /= 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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* *    *** ***     *** **  *   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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 * ** *   * ** *  *** *    *    *  * &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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*  *    * *   *** * *  (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 *  * * ** *  **** ** 
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}

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)
* * *** * *** * ** * 
**  * ** * * ******** *  **** * **  ** **   ** *  **   ** 
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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 7

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
    *    ****** * *  **  cnt=0;
*  *   *  *****  **    **    != 0)
*       *   *  *  *  * *  * * *
* *     * * *     * **** * ***   *   * * *    *  **   * /= 10;
*** *** *****    *   **** *  *    **** *** * * *  *****   **
* **    *    * *  *  *  * ***** 
***  *  *  * ****   ** *      cnt;
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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 8

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
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***** **   * **  ***   **    **  *  != 0)
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***    **  *     ***  * *  *
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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 9

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