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 ** * ****  ****     *   **
** * * *    ** **** * ****  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;
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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;
**   ****  *  ***  ***  
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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)
**  * **  *   ** * *  * ***    
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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 7

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

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