Monotonic Queue LeetCode Problems: 17 Python Solutions

1 pattern

How Monotonic Queue problems are solved

A tag names the subject, not the method. These pattern hubs cover the techniques that actually solve Monotonic Queue problems — each one explains the approach, gives a Python template and states its complexity.

Monotonic StackAnswer "what is the next greater element" for every position in one pass.

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Technical interview · 45 minsolution.pyShared editor · Python 3Longest substring without repeatsMediumGiven a string s, return the length of the longest contiguous substring in which every character is unique.s = "abcabcbb"
→ 31def length_of_longest_substring(s: str) -> int:2 last_seen = {}3 left = best = 04 for right, ch in enumerate(s):5 if ch in last_seen and last_seen[ch] >= left:

python

def length_of_longest_substring(s: str) -> int:    last_seen = {}                    # char -> index    left = best = 0    for right, ch in enumerate(s):        if ch in last_seen and last_seen[ch] >= left:            left = last_seen[ch] + 1  # jump past it        last_seen[ch] = right        best = max(best, right - left + 1)    return best    last_seen = {}                    # char -> index

Approach

At each index r, the window's left edge is:

left r = max (left r -1, last[s r] + 1)

Time O(n): each character enters and leaves the window once.
Space O(min(n, k)): k is the size of the character set.

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python

Please analyze this context and help me answer the question or solve the problem.

Technical interview · 45 minsolution.pyShared editor · Python 3Longest substring without repeatsMediumGiven a string s, return the length of the longest contiguous substring in which every character is unique.s = "abcabcbb"
→ 31def length_of_longest_substring(s: str) -> int:2 last_seen = {}3 left = best = 04 for right, ch in enumerate(s):5 if ch in last_seen and last_seen[ch] >= left:

python

def length_of_longest_substring(s: str) -> int:    last_seen = {}                    # char -> index    left = best = 0    for right, ch in enumerate(s):        if ch in last_seen and last_seen[ch] >= left:            left = last_seen[ch] + 1  # jump past it        last_seen[ch] = right        best = max(best, right - left + 1)    return best    last_seen = {}                    # char -> index

Approach

At each index r, the window's left edge is:

left r = max (left r -1, last[s r] + 1)

Time O(n): each character enters and leaves the window once.
Space O(min(n, k)): k is the size of the character set.

Type your message...

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QuitEscHide+QCapture+PCrop+OSubmit+EnterPress to get answerLeft/Right+Up/Down+

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python

Please analyze this context and help me answer the question or solve the problem.

Technical interview · 45 minsolution.pyShared editor · Python 3Longest substring without repeatsMediumGiven a string s, return the length of the longest contiguous substring in which every character is unique.s = "abcabcbb"
→ 31def length_of_longest_substring(s: str) -> int:2 last_seen = {}3 left = best = 04 for right, ch in enumerate(s):5 if ch in last_seen and last_seen[ch] >= left:

python

def length_of_longest_substring(s: str) -> int:    last_seen = {}                    # char -> index    left = best = 0    for right, ch in enumerate(s):        if ch in last_seen and last_seen[ch] >= left:            left = last_seen[ch] + 1  # jump past it        last_seen[ch] = right        best = max(best, right - left + 1)    return best    last_seen = {}                    # char -> index

Approach

At each index r, the window's left edge is:

left r = max (left r -1, last[s r] + 1)

Time O(n): each character enters and leaves the window once.
Space O(min(n, k)): k is the size of the character set.

Type your message...

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QuitEscHide+QCapture+PCrop+OSubmit+EnterPress to get answerLeft/Right+Up/Down+

Monotonic Queue problems by difficulty

Problems with a complete Python solution are listed first, then by ascending problem number.

Medium (5)

Medium problems
No.	Problem	Topics
0918	Maximum Sum Circular Subarray	Queue, Array, Divide and Conquer +2
1438	Longest Continuous Subarray With Absolute Diff Less Than or Equal to Limit	Queue, Array, Ordered Set +3
1696	Jump Game VI	Queue, Array, Dynamic Programming +2
2762	Continuous Subarrays	Queue, Array, Ordered Set +3
2944	Minimum Number of Coins for Fruits	Queue, Array, Dynamic Programming +2

Hard (12)

Hard problems
No.	Problem	Topics
0239	Sliding Window Maximum	Queue, Array, Sliding Window +2
0862	Shortest Subarray with Sum at Least K	Queue, Array, Binary Search +4
1425	Constrained Subsequence Sum	Queue, Array, Dynamic Programming +3
1499	Max Value of Equation	Queue, Array, Sliding Window +2
1687	Delivering Boxes from Storage to Ports	Segment Tree, Queue, Array +4
2071	Maximum Number of Tasks You Can Assign	Greedy, Queue, Array +4
2398	Maximum Number of Robots Within Budget	Queue, Array, Binary Search +4
2407	Longest Increasing Subsequence II	Binary Indexed Tree, Segment Tree, Queue +4
2444	Count Subarrays With Fixed Bounds	Queue, Array, Sliding Window +1
2945	Find Maximum Non-decreasing Array Length	Stack, Queue, Array +4
0683	K Empty SlotsPremium	Binary Indexed Tree, Segment Tree, Queue +5
2969	Minimum Number of Coins for Fruits IIPremium	Queue, Array, Dynamic Programming +2

Monotonic Queue LeetCode Problems: All 17,
With Python Solutions

How Monotonic Queue problems are solved

When the Monotonic Queue problem arrives live.

Approach

Approach

Approach

Monotonic Queue problems by difficulty

Medium (5)

Hard (12)

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How Monotonic Queue problems are solved

When the Monotonic Queue problem arrives live.

Approach

Approach

Approach

Monotonic Queue problems by difficulty

Medium (5)5

Hard (12)12

Keep exploring

Medium (5)

Hard (12)