【leetcode每日刷題】480. Sliding Window Median

https://leetcode.com/problems/sliding-window-median/

使用最小堆+最大堆的方法實現，中位數實現的一種方法。

import java.util.Collection;
import java.util.Collections;
import java.util.PriorityQueue;

class Solution {
    public double[] medianSlidingWindow(int[] nums, int k) {
        if(nums == null || nums.length == 0) return new double[0];
        double[] result = new double[nums.length-k+1];
        PriorityQueue<Integer> left = new PriorityQueue<>(Collections.reverseOrder());
        PriorityQueue<Integer> right = new PriorityQueue<>();
        for(int i=0; i<nums.length; i++){
            if(left.size()<=right.size()){
                right.add(nums[i]);
                left.add(right.poll());
            }else{
                left.offer(nums[i]);
                right.offer(left.poll());
            }
            if(left.size() + right.size() == k){
                double mid = 0;
                if(left.size() > right.size()){
                    mid = left.peek();
                }else{
                    mid = ((long)left.peek()+(long)right.peek())/2.0;
                }
                int index = i-k+1;
                result[index] = mid;
                if(!left.remove(nums[index])){
                    right.remove(nums[index]);
                }
            }
        }
        return result;
    }
}