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

int main(void)
{
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** * * *  * **  * ** ** *   *  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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}

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{
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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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}



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{
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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)
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for (divisor  ** ** **   **   **  *  * 
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return true;
}
int main(void)
{
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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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**    ***   * **     ** **** 1;
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}

int main(void)
{
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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)
{
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* ***** *** * * *** ** **  **** != 0)
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*  ***  ***  *  ** *** **** *  *
*  ** *****   **** ** *  **  *  count;
}

int main(void)
{
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  **  **  ** **   **** *  * *****  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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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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}

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*/
** *****    ******* ***
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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'