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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}

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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*  * *** * * **** ***** ** ***   has %d *  * * *      **** *  * *
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}

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 *  *  ** **   * ***** *** *
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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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}

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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}

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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* **   *  * *   * ** **  ***  **  cnt;
* ******   **  *   ** ***  *

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 8

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