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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*   * ****  **** * **   * * * count;
}

int main(void)
{
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* * * *  * **  *    ***  *   ****  **    * has %d  * ** ***      ** *  
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}

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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   *  ** ** * * * *   *   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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***  * * *  *  ***   *  **     ***      &n);
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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 *  *  ****** * *   ** *  
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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)
{
**  ***      * *** * **   count=0;
* * *     * **    * *   **      != 0)
*   *** *    * ***** 
* *  *  * * ***      ** *  ***  * *  * *  *  ** * ****** ****
* *** ***  ** * * **  *** *     **  **  **  ** **  **   *   /= 10;
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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 7

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
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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 8

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 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)
{
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** ** *   * ** * **   *  *  * ** ****  &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'