Documentation Index

Fetch the complete documentation index at: https://swe.aboneda.com/llms.txt

Use this file to discover all available pages before exploring further.

​

Monotonic Stack & Queue

​

Monotonic Stack

​

How It Works

• When pushing a new element, pop all elements that violate the monotonic property
• The popped elements have “found” their answer (the current element)

​

Types

• Monotonically Increasing — finds next smaller element
• Monotonically Decreasing — finds next greater element

​

Template (Next Greater Element)

def next_greater(nums):
    n = len(nums)
    result = [-1] * n
    stack = []  # stores indices
    for i in range(n):
        while stack and nums[stack[-1]] < nums[i]:
            result[stack.pop()] = nums[i]
        stack.append(i)
    return result

​

Time & Space: O(n) each

​

Monotonic Deque (Queue)

​

Template (Sliding Window Maximum)

from collections import deque

def max_sliding_window(nums, k):
    dq = deque()  # stores indices, decreasing order of values
    result = []
    for i in range(len(nums)):
        while dq and dq[0] < i - k + 1:
            dq.popleft()
        while dq and nums[dq[-1]] < nums[i]:
            dq.pop()
        dq.append(i)
        if i >= k - 1:
            result.append(nums[dq[0]])
    return result

​

Classic Problems

• Next Greater Element I, II
• Daily Temperatures
• Largest Rectangle in Histogram
• Trapping Rain Water
• Sliding Window Maximum
• Shortest Subarray with Sum at Least K
• Stock Span Problem
• Remove K Digits

​

When to Use

• “Next greater/smaller element” patterns
• Sliding window min/max queries
• Histogram-based area problems
• Problems requiring efficient range extrema