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239. Sliding Window Maximum

HardOpen on LeetCodeProblem statement

Problem Statement

239. Sliding Window Maximum

Hard


You are given an array of integers 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 1:

Input: nums = [1,3,-1,-3,5,3,6,7], 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

Example 2:

Input: nums = [1], k = 1
Output: [1]

 

Constraints:

C++

Source file
class Solution {
public:
    struct comparator{
        bool operator()(pair<int, int> a, pair<int, int> b){
            return a.first<b.first;
        }
    };
    
    vector<int> maxSlidingWindow(vector<int>& nums, int k) {
        if(k==1)
            return nums;
        vector<int> res;
        priority_queue<pair<int, int>, vector<pair<int, int>>, comparator> pq;
        for(int i=0; i<k; i++)
            pq.push({nums[i], i});
        res.push_back(pq.top().first);
        for(int i=k; i<nums.size(); i++){
            while(pq.top().second<=i-k)
                pq.pop();
            pq.push({nums[i], i});
            res.push_back(pq.top().first);
        }
        return res;
    }
};