HardLeetCode #239Sliding Window

Sliding Window Maximum

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.

Constraints

1 <= nums.length <= 10^5, -10^4 <= nums[i] <= 10^4, 1 <= k <= nums.length

Examples

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

Output: [3,3,5,5,6,7]

Solution Approach

Maintain a window of elements with a specific property. Expand window by moving right pointer, contract by moving left pointer when condition is violated. Use HashMap/Set to track elements in current window.

Implementation

def lengthOfLongestSubstring(s):
    char_map = {}
    max_length = 0
    left = 0
    for right in range(len(s)):
        if s[right] in char_map:
            left = max(left, char_map[s[right]] + 1)
        char_map[s[right]] = right
        max_length = max(max_length, right - left + 1)
    return max_length

Complexity Analysis

Time Complexity

O(n)

Space Complexity

O(min(m, n))

Key Learning Points

Maintain valid window with two pointersUse HashMap for character trackingExpand right, contract left when needed