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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 *  ** *** * *** ***
    ***      *** ***  *  *  * **  ***    count;
}

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 2

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#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

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#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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}

int main(void)
{
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* *** *  * * *    *  **** 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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}

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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}
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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**  *   *  * *  ** * ** * ***  * *
* *** * * ******  * **   * 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'