Last week i was breaking my head to get the solution for this Practical Number. In beginning it was taught to even understand what it is. Later i found the meaning of Practical Number from Wikipedia. My problem is to print list of practical number within a range. After some workout I got the solution to be like this,
import java.util.*;
public class PracticalNumbers {
public int[] getPracticalNumbers(int from, int to) {
ArrayList<Integer> result = new ArrayList<Integer>();
ArrayList<Integer> divisor = new ArrayList<Integer>();
for(int i=from;i<=to;i++)
{
if(check4Practical(i))
{
result.add(i);
}
}
int []res=new int[result.size()];
for(int i=0;i<result.size();i++)
{
res[i]=result.get(i).intValue();
}
if(res.length>0)
{
return res;
}
return new int[]{};
}
boolean check4Practical(Integer num)
{
ArrayList<Integer> divisors = new ArrayList<Integer>();
for(int i=1;i<num;i++){
if(num%i == 0)
{
divisors.add(i);
}
}
int[] divisors_arr = new int[divisors.size()];
for(int i =0;i<divisors_arr.length;i++)
{
divisors_arr[i] = divisors.get(i).intValue();
}
for(int i = num-1;i>0;i--)
{
int temp = i;
for(int j= divisors_arr.length-1;j>=0;j--)
{
if(temp>0)
temp -= divisors_arr[j];
if(temp <0)
temp+= divisors_arr[j];
if(temp == 0)
break;
}
if(temp!= 0 )
return false;
}
return true;
}
public static void main(String[] arg) {
PracticalNumbers pn = new PracticalNumbers();
//test case
int[] res = pn.getPracticalNumbers(1, 200);
for (int i = 0; i < res.length; i++)
System.out.print(res[i] + " ");
}
}
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