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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}

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

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 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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}
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'