// 方法一、优先队列
class Solution {
public:
    vector<int> maxSlidingWindow(vector<int>& nums, int k) {
        int n = nums.size();
        priority_queue<pair<int, int>> q;
        for(int i = 0; i < k; i++){
            q.emplace(nums[i], i);
        }
        vector<int> ans = {q.top().first};
        for(int i = k; i < n; i++){
            q.emplace(nums[i], i);
            while(q.top().second <= (i - k)){
                q.pop();
            }
            ans.push_back(q.top().first);
        }
        return ans;
    }
};

// 方法二、单调队列
class Solution {
public:
    vector<int> maxSlidingWindow(vector<int>& nums, int k) {
        int n = nums.size();
        deque<int> q; 
        vector<int> ans;
        for(int i = 0; i < k; i++){
            while(!q.empty() && nums[i] >= nums[q.back()]){
                q.pop_back();
            }
            q.push_back(i);
        }
        ans.push_back(nums[q.front()]);
        for(int i = k; i < n; i++){
            while(!q.empty() && nums[i] >= nums[q.back()]){
                q.pop_back();
            }
            q.push_back(i);
            while(q.front() <= i - k){
                q.pop_front();
            }
            ans.push_back(nums[q.front()]);
        }
        return ans;
    }
};