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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}

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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*  ***  **  *    * ** *     * *   *     ***    &n);
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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)
{
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if (n<=1)
*** ***   *   * *  false;
for (divisor     * ***** *   **   * ****
*    ** * * **    * **** **   
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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*** *** *  ** ** * *  *
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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)
**  * *  ***    ***   * 
** * *  **    * *** ** *** ***    ** *    *  *** **  *    ***
* ** *** * *    ***     **** *  **  **  ** *  /= 10;
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}

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 7

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
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**  * ** ** *  **      *  **  != 0)
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**       * ** * *   ** *****  * cnt;
  *   **    * * * *   ***

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)
{
*** ***  ** * * *  **   ** count=0;
 *  **    * **   ** *  ** *   **
*  *   *   **  **     != 0)
**  * * * *  *     * 
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 ***  *    *      **      ** * * ***  **** * *      *   **   * ** ++;
****  *  * *  ****  *
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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 9

Hidden content!
int num_digits(int n)
{
*** *     * ***      **     num_digit=0;/*INSERT YOUR CODE HERE*/
 ****  * **** * *** * ****  
 *  *   **** * * * **  *
   **   **     *    *** *  ****     ** **  * * * ** ******
* ** *  * *  * * ******* ** ******  *   *   *****   * 
** *   ****  ***  * ** 

**  ** *** ****  *  *** *   *     *  *
 **  ******  *** *   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*/
   *   ***  ** *** **** * *** *
  **** ** *  **
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** ** *** ** **    **   *  *  * *    *    ***  ** 
* ** ***  * *   * * 

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