Day 1: Interquartile Range

import java.io.*;
import java.util.*;

public class Solution {

    public static void main(String[] args) {
        /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */
        Scanner scan = new Scanner(System.in);
        int n = scan.nextInt();
        int[] x = new int[n];
        int[] f = new int[n];
        int sum = 0;
        for(int i=0;i<n;i++)
            x[i] = scan.nextInt();
        for(int i=0;i<n;i++){
            f[i] = scan.nextInt();
            sum = sum + f[i];
        }
        int[] s = new int[sum];
        boolean isSorted = false;
        int lastIndex = n-1;
        while(!isSorted){
            isSorted = true;
            for(int i=0;i<lastIndex;i++){
                if(x[i]>x[i+1]){
                    int temp;
                    temp = x[i];
                    x[i] = x[i+1];
                    x[i+1] = temp;
                    int temp1;
                    temp1 = f[i];
                    f[i] = f[i+1];
                    f[i+1] = temp1;
                    isSorted = false;
                }
            }
        }
        int j = 0;
        float q1,q2,q3;
        for(int i=0;i<n;i++){
            while(f[i]>0 && j<sum){
                s[j] = x[i];
                j++;
                f[i]--;
            }
        }
        if(sum%2==0){
            q2 = (s[sum/2-1] + s[sum/2])/2;
            if((sum/2)%2==0){//over
                q1 = (s[sum/4] + s[sum/4-1])/2;
                q3 = (s[sum/4 + sum/2] + s[sum/4 + sum/2 -1])/2;
            }
            else{//over
                q1 = s[sum/2-sum/4-1];
                q3 = s[sum/2+sum/4];
            }
        }
        else{
            q2 = s[sum/2];
            if((sum/2)%2==0){//over
                q1 = (s[sum/4] + s[sum/4-1])/2;
                q3 = (s[sum/4 + sum/2] + s[sum/4 + sum/2 +1])/2;
            }
            else{//over
                q1 = s[sum/2-sum/4-1];
                q3 = s[sum/2+sum/4+1];
            }
        }
        System.out.printf("%.1f",q3-q1);
    }
}