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

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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}

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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}

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)
{
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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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** *  *  *   *  **  *    *
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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;
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** ***   *    ** ** **** *  **  * *** **   * *** **
*  *  *** *  **     * * * ** * **  ***   * *   ** **  * * /= 10;
***  * * **  ******** 
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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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*  ***   ***   ***     *  * ****  != 0)
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*   **** *      *** **  *  * **

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 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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*** *  **   ** * *   *   *** ***  *  *    *** &n);
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***  * ***  **   *    ** ****   *** 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*/
 ***  * *** ***  *** *** * 
 *  **  *****      
*  * *  * * *     * **  * ** ** * * *  *** * **
 * *  *  *   **  *  ** * *** **  *** *  **  *** *   
 * **** *** * **   * 

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