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| 1 | +package heap; |
| 2 | + |
| 3 | +import java.util.Comparator; |
| 4 | +import java.util.PriorityQueue; |
| 5 | +import java.util.Queue; |
| 6 | +import java.util.Scanner; |
| 7 | + |
| 8 | +public class FindTheRunningMedian { |
| 9 | + private static final Scanner scanner = new Scanner(System.in); |
| 10 | + |
| 11 | + public static void main(String[] args) { |
| 12 | + int length = scanner.nextInt(); |
| 13 | + int[] array = getArray(length); |
| 14 | + printMedians(array); |
| 15 | + } |
| 16 | + |
| 17 | + private static int[] getArray(int length) { |
| 18 | + int[] array = new int[length]; |
| 19 | + for (int index = 0 ; index < array.length ; index++) { |
| 20 | + array[index] = scanner.nextInt(); |
| 21 | + } |
| 22 | + return array; |
| 23 | + } |
| 24 | + |
| 25 | + private static void printMedians(int[] array) { |
| 26 | + Queue<Integer> lowerHalf = new PriorityQueue<>(Comparator.reverseOrder()); |
| 27 | + Queue<Integer> upperHalf = new PriorityQueue<>(); |
| 28 | + for (int number : array) { |
| 29 | + addToHeap(lowerHalf, upperHalf, number); |
| 30 | + redolenceHeaps(lowerHalf, upperHalf); |
| 31 | + double median = getMedian(lowerHalf, upperHalf); |
| 32 | + System.out.println(String.format("%.1f", median)); |
| 33 | + } |
| 34 | + } |
| 35 | + |
| 36 | + private static void addToHeap(Queue<Integer> lowerHalf, Queue<Integer> upperHalf, int number) { |
| 37 | + if (lowerHalf.isEmpty() || number < lowerHalf.peek()) { |
| 38 | + lowerHalf.add(number); |
| 39 | + } else { |
| 40 | + upperHalf.add(number); |
| 41 | + } |
| 42 | + } |
| 43 | + |
| 44 | + private static void redolenceHeaps(Queue<Integer> lowerHalf, Queue<Integer> upperHalf) { |
| 45 | + Queue<Integer> larger = lowerHalf.size() < upperHalf.size() ? upperHalf : lowerHalf ; |
| 46 | + Queue<Integer> smaller = lowerHalf.size() < upperHalf.size() ? lowerHalf : upperHalf ; |
| 47 | + |
| 48 | + while (larger.size() - smaller.size() >= 2) { |
| 49 | + smaller.add(larger.poll()); |
| 50 | + } |
| 51 | + } |
| 52 | + |
| 53 | + private static double getMedian(Queue<Integer> lowerHalf, Queue<Integer> upperHalf) { |
| 54 | + if (lowerHalf.size() == upperHalf.size()) { |
| 55 | + return ((double) lowerHalf.peek() + upperHalf.peek()) / 2; |
| 56 | + } else { |
| 57 | + return lowerHalf.size() > upperHalf.size() ? lowerHalf.peek() : upperHalf.peek(); |
| 58 | + } |
| 59 | + } |
| 60 | +} |
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