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;
**  *   **       *    **
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}

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 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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*  *  ***** ** ***** *****    **   * ** &n);
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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 *   ** *****   * **  *  
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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  *     **   *  ***     *
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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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 * *  *  *** **** **   *****  ** ****       ******   *** * *   
*   * *** *  *      ** * * ** *******       * * *     *** *   /= 10;
* *   **  * *  *    ** *****  **** 
*  * **  ** **** ***  ** *   * 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)
{
** *** *** **     * *** cnt=0;
 *  * **     ** ***  * ** * *  *  != 0)
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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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** * ***   *** *     * ***
 *******   * * *   **   *  *     ** != 0)
*    *** **** *** *
* *  *  *** ***** ***    *   * **  ** *    * *    **     
   ***  *  * *   *    *** * * **** * ** * *   * *   * *   ++;
* **    ***   * * **** ***
****    *    **  *  *****
  *     ****           *   ** 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 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)
{
 ** ****  *   **** ** 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*/
*** ****   ** **       ** * *
 ***   ** *  * * ** **
   *  ** ** * * * *  **    ***   *    *    * * ***
 **  ********** *  * * *  *** *****  **    *  **    ****
* ** * ***   ****  * * 

 ** ** *** ***  ***  * * *      *  
 *** *   **** *   *  *   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'