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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* *        ** *  * *    **  ** 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 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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* *  * ** * *** ** * *** *   * ****  &n);
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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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}

int main(void)
{
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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)
{
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*  *** **  * *****    *     *      != 0)
* ** **   **** *** * *** *  
**** **   **  **   ****  *    *  *  *****  * *   **  ** * 
* * *****       ** ****  ** ***  * *    * ***     ** *  /= 10;
 *  ***   * * ***   ***     
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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 7

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 8

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
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* ***   ***** * *  *   *    
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*  *  *  *     ** *  * * ** * ** 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 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'