/*
* @lc app=leetcode id=239 lang=cpp
*
* [239] Sliding Window Maximum
*
* https://leetcode.com/problems/sliding-window-maximum/description/
*
* algorithms
* Hard (39.10%)
* Likes: 2011
* Dislikes: 118
* Total Accepted: 180.1K
* Total Submissions: 460.2K
* Testcase Example: '[1,3,-1,-3,5,3,6,7]\n3'
*
* Given an array nums, there is a sliding window of size k which is moving
* from the very left of the array to the very right. You can only see the k
* numbers in the window. Each time the sliding window moves right by one
* position. Return the max sliding window.
*
* Example:
*
*
* Input: nums = [1,3,-1,-3,5,3,6,7], and k = 3
* Output: [3,3,5,5,6,7]
* Explanation:
*
* Window position Max
* --------------- -----
* [1 3 -1] -3 5 3 6 7 3
* 1 [3 -1 -3] 5 3 6 7 3
* 1 3 [-1 -3 5] 3 6 7 5
* 1 3 -1 [-3 5 3] 6 7 5
* 1 3 -1 -3 [5 3 6] 7 6
* 1 3 -1 -3 5 [3 6 7] 7
*
*
* Note:
* You may assume k is always valid, 1 ≤ k ≤ input array's size for non-empty
* array.
*
* Follow up:
* Could you solve it in linear time?
*/
class Solution {
public:
vector<int> maxSlidingWindow(vector<int>& nums, int k) {
deque<int> q;
vector<int> res;
for (int i = 0; i < nums.size(); ++i) {
while (!q.empty() && nums[i] > q.back()) q.pop_back();
q.push_back(nums[i]);
const int f = i - k + 1;
if (f < 0) continue;
res.push_back(q.front());
if (nums[f] == q.front()) q.pop_front();
}
return res;
}
};