https://leetcode.com/problems/sliding-window-maximum/description/
//双向单调队列
class Solution {
public:
vector<int> maxSlidingWindow(vector<int>& nums, int k) {
//双向队列是从大到小的 单调队列
vector<int> res;
deque<int> Q;
for(int i=0; i<nums.size(); i++){
if(!Q.empty() && Q.front() == i-k) Q.pop_front(); //队列中队首元素到当前的位置差是不是大于K,
while (!Q.empty() && nums[Q.back()] < nums[i]) {
Q.pop_back();
}
Q.push_back(i);
if(i >= k-1) res.push_back(nums[Q.front()]);
}
return res;
}
};