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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*** * * ****    *** * * * * *   * 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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* ****  ** * **   **  * **     * has %d   ** * ** *****     ****   *
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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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*** ** *** *     ***  ** ** **** * **  *       *  **  **    
*   * *   *  *  * ** ****  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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 * ***  *  *** * * ** **  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)
{
*  *   * ******     *   count=0;
 *    **       * * ** ***        != 0)
*  **  * *** *  * ** *  ****  
 *  *** *   ****  *  *    **  *          * *   **      
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* ****  *  * *** * *  * * **   
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}

int main(void)
{
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*  **     *    **  *  *** *  **  * * *** *  * *   &n);
***  **    * ** *     * ** *   * * *** has %d *  *    ********* **  ** 
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}

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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*   ****** ******* * **  ** 
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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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*      ** *   *   *  ** *** 
 * *   **  *  *  **** **  ** * * != 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 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*/
 * ******  * *  *** * *    
* * *      * *  *  ** 
  **   *  *    **** **  ****  **** * *  * ****  *  
 * *       * *  *   ***** * **** *** * * *     *     
* *  ** ***    **

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