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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* * *  ** *  ** ****  * * **  *  ** * **  * * ***   /= 10;
**** *   *** **   ***  **  
*  * * *  **  * *  *     *   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  **    *   ** ** ** **   *
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}

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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****  * **  ** *  * ** (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)
{
*** * ***** **       *  *  *** 
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}

int main(void)
{
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** * **** * ***    * **  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)
{
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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;
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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)
{
* ** * * ****  * *** *      *** count=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*/
**   * ****   ****       *   **
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*  *  ***   ** * ********  ***  ****** *  ** **  **
 *  *       **  ******* * * ** ***  ***  *   *   *
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   *** * ** *  ***   * *    * * *  ** **  * 
*   *  * * * **     ***  * 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'