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)
{
**        *   * ** ***       count=0;
*  **  * **   ** * *** * ***  **    != 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 2

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 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)
{
**** **  *  **  ****** * * * *
** **** *     ** * * *** * * 1;
** **  * ****** *** * *
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}

int main(void)
{
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* * *** *        *    *  *   *  ***  &n);
*** * * * * **   *   * *     *** * * 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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*  ****    ** * * * * **** ****
* *   ** * ******  ***** ***** *   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 7

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

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

 **      *     * *   ** * * *  ****
  *** ***  *** *      *    *   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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     *** * ** *** *  ** * *  *   ** **  *    ** **      *
 ***  ********     **

**  *    ** **** **   *  ** *  * * **   * ** 
** *  ** *  ** * *  * OF YOUR CODE*/
**** * * *   * *  * ** *** count;
}

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'