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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*  ** ** *  *  *    *  ******  != 0)
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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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* **** ** *  *      *    *   ** ***** has %d ** * * ***   *  ***  ** * 
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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)
{
*   * * **************  divisor;
if (n<=1)
 * ** * *  *** * ** false;
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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**   *    * * ** 
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}

int main(void)
{
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*   * **   *  *  * * **   * * * *** *  *   *  &n);
*    *  *  ** **  * *  **  *  * * 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)
{
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* *   *   ***    **** **** != 0)
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** *  *        * **    *  *
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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)
{
*     ********   * **    * *  cnt=0;
*  *** **      ** *        != 0)
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* * *** **** *  * ** *  ** *** * *  cnt;
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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)
{
**    *** ** * ** * ** ** ** count=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*/
*   *  * *   **   **    * 
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**** **         *  ***  * * ****   **** **    **  * 
****   ********  ** *** *** **** ** *          **  
 ****   ** *   *  * 

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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'