每天一道剑指offer-滑动窗口的最大值

public ArrayList<Integer> maxInWindows(int [] num, int size){
}

public ArrayList<Integer> maxInWindows(int [] num, int size){    ArrayList<Integer> res = new ArrayList();    if(num == null || num.length == 0 || size <= 0 || size > num.length){        return res;    }
    //用队头元素保存窗口最大值，队列中元素只能是单调递减的，窗口移动可能导致队头元素失效    LinkedList<Integer> queue = new LinkedList();    int start = 0, end = size - 1;    for(int i = start ; i <= end ; i++){        addLast(queue, num[i]);    }    res.add(queue.getFirst());    //移动窗口    while(end < num.length - 1){        addLast(queue, num[++end]);        if(queue.getFirst() == num[start]){            queue.pollFirst();        }        start++;        res.add(queue.getFirst());    }
    return res;}
public void addLast(LinkedList<Integer> queue, int num){    if(queue == null){        return;    }    //加元素之前要确保该元素小于等于队尾元素    while(queue.size() != 0 && num > queue.getLast()){        queue.pollLast();    }    queue.addLast(num);}