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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}

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 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

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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: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)
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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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* **  ****  *  ** * *** ********    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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*  ***** * ** *******    **** * ** *    *  **  **** **  *   *  *
**   *  * ** ****   **** ***  ** *** * *        *     ** /= 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 7

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
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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 8

Hidden content!
#include <stdio.h>
int num_digits(int n)
{
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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)
{
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 **     *   *   *   *  *    *** * ** has %d  * ********   *** * *** * **
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}

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'