1438. Longest Continuous Subarray With Absolute Diff Less Than or Equal to Limit

class Solution:
    def longestSubarray(self, A: List[int], limit: int) -> int:
        # main idea: convert diff of any two elements within array <= limit ==> diff between min and max elments of subarray   
        # time O(N) space O(N)
        maxd = collections.deque() # monotonically decreasing order by index 
        mind = collections.deque() # monotonically increasing order by index
        l = 0
        res = 1
        n = len(A)
        for r in range(n):
            while len(maxd) and A[r] > maxd[-1]: maxd.pop()
            while len(mind) and A[r] < mind[-1]: mind.pop()
            maxd.append(A[r])
            mind.append(A[r])
            # shrink left ptr if diff exceed limit
            while maxd[0] - mind[0] > limit: #  left ptr move forward ,but it may affect maxd and mind since elements on left of l will be discarded.
                if maxd[0] == A[l]:maxd.popleft() # maxd[0] is the max number in maxd 
                if mind[0] == A[l]:mind.popleft() # maxd[0] is the smallest number in mind 
                l += 1
            res = max(res,r-l+1)
        return res