239 滑动窗口最大值

https://leetcode.cn/leetbook/read/top-interview-questions-hard/xw4q0r/

cost: NaN

class Solution {
public:
    vector<int> maxSlidingWindow(vector<int>& nums, int k) {
        vector<int> res;
        deque<int> q;
        for (int i = 0; i < k; i++) {
            while (!q.empty() && nums[q.back()] <= nums[i]) {
                q.pop_back();
            }
            q.push_back(i);
        }
        res.push_back(nums[q.front()]);
        for (int i = k; i < nums.size(); i++) {
            if (q.front() <= i - k) {
                q.pop_front();
            }
            while (!q.empty() && nums[q.back()] <= nums[i]) {
                q.pop_back();
            }
            q.push_back(i);
            res.push_back(nums[q.front()]);
        }
        return res;
    }
};