LeetCode-in-Swift
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]
Example 3:
Input: nums = [1,-1], k = 1
Output: [1,-1]
Example 4:
Input: nums = [9,11], k = 2
Output: [11]
Example 5:
Input: nums = [4,-2], k = 2
Output: [4]
Constraints:
1 <= nums.length <= 105-104 <= nums[i] <= 1041 <= k <= nums.length
Solution
import Collections
class Solution {
func maxSlidingWindow(_ nums: [Int], _ k: Int) -> [Int]
{
// monontonic decreasing queue, storing indexes of nums
var queue = Deque<Int>()
var ans: [Int] = []
for i in 0..<nums.count
{
// mantain window size no bigger then k
while !queue.isEmpty && i - queue.first! >= k {
queue.removeFirst()
}
// mantain queue monotonic decreasing
while !queue.isEmpty && nums[queue.last!] < nums[i] {
queue.removeLast()
}
queue.append(i)
if i >= k-1 {
ans.append(nums[queue.first!]) // max value in window
}
}
return ans
}
}