【剑指Offer】59. 1滑动窗口的最大值

import java.util.*;
import java.lang.*;
public class Solution {
    public ArrayList<Integer> maxInWindows(int[] num, int size) {
        ArrayList<Integer> res = new ArrayList<>();
        if(num.length == 0 || size == 0)
            return res;
        
        Deque<Integer> q = new LinkedList<>();
        int index = 0;
        
        for(int i = 0; i < num.length; i++) {
            // 队列存下标，控制出队的几种情况 1 3 -1 -3 5
            // q[3 -1 -3 5]出3
            if(q.size() > 0 && i - q.peekFirst() >= size) 
                q.pollFirst();
            // q[-1 -3 5]出 -3 -1
            while(q.size() > 0 && num[i] > num[q.peekLast()])
                q.pollLast();
            q.add(i);
            // 最大值放入
            if(i >= size - 1)
                res.add(num[q.peekFirst()]);
        }
        
        return res;
    }
}

public ArrayList<Integer> maxInWindows(int[] num, int size) {
    ArrayList<Integer> ret = new ArrayList<>();
    if (size > num.length || size < 1)
        return ret;
    PriorityQueue<Integer> heap = new PriorityQueue<>((o1, o2) -> o2 - o1);  /* 大顶堆 */
    for (int i = 0; i < size; i++)
        heap.add(num[i]);
    ret.add(heap.peek());
    for (int i = 0, j = i + size; j < num.length; i++, j++) {            /* 维护一个大小为 size 的大顶堆 */
        heap.remove(num[i]);
        heap.add(num[j]);
        ret.add(heap.peek());
    }
    return ret;
}