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;
*    * ** *   * ****** ********
**  *    *     ** *****  * 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  * *  *  **   *    * ** 
* * ** ** *  * * **  ** 
return true;
}
int main(void)
{
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***  * * ** * * ***    * *  ****  *  **   &n);
*  *    *  *  **** *  * ** (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  *    * ** * ***  ****  *   *
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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)
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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)
{
*** ** *** *   *  * ***  **  * cnt=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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***   *  * *   *      * *   *  **
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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 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'