Queue LeetCode Problems: 43 Python Solutions

1 pattern

How Queue problems are solved

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

StackWhen the most recent unresolved thing is the one that matters, use a stack.

Eyes only

When the Queue problem arrives live.

In the live round, Stealth Interview reads the problem off your screen, returns a working solution with a step-by-step explanation and its time and space complexity, and transcribes what the interviewer says. It's a desktop app for macOS and Windows, invisible to screen sharing.

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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.

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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+

90%Subscription

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+

Queue problems by difficulty

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

Easy (7)

Easy problems
No.	Problem	Topics
0225	Implement Stack using Queues	Stack, Design, Queue
0232	Implement Queue using Stacks	Stack, Design, Queue
0387	First Unique Character in a String	Queue, Hash Table, String +1
0933	Number of Recent Calls	Design, Queue, Data Stream
1700	Number of Students Unable to Eat Lunch	Stack, Queue, Array +1
2073	Time Needed to Buy Tickets	Queue, Array, Simulation
0346	Moving Average from Data StreamPremium	Design, Queue, Array +1

Medium (19)

Medium problems
No.	Problem	Topics
0341	Flatten Nested List Iterator	Stack, Tree, Depth-First Search +3
0622	Design Circular Queue	Design, Queue, Array +1
0641	Design Circular Deque	Design, Queue, Array +1
0649	Dota2 Senate	Greedy, Queue, String
0918	Maximum Sum Circular Subarray	Queue, Array, Divide and Conquer +2
0950	Reveal Cards In Increasing Order	Queue, Array, Sorting +1
1438	Longest Continuous Subarray With Absolute Diff Less Than or Equal to Limit	Queue, Array, Ordered Set +3
1670	Design Front Middle Back Queue	Design, Queue, Array +2
1696	Jump Game VI	Queue, Array, Dynamic Programming +2
1823	Find the Winner of the Circular Game	Recursion, Queue, Array +2
2327	Number of People Aware of a Secret	Queue, Dynamic Programming, Simulation
2526	Find Consecutive Integers from a Data Stream	Design, Queue, Hash Table +2
2762	Continuous Subarrays	Queue, Array, Ordered Set +3
2944	Minimum Number of Coins for Fruits	Queue, Array, Dynamic Programming +2
0281	Zigzag IteratorPremium	Design, Queue, Array +1
0353	Design Snake GamePremium	Design, Queue, Array +2
0362	Design Hit CounterPremium	Design, Queue, Array +2
0379	Design Phone DirectoryPremium	Design, Queue, Array +2
1429	First Unique NumberPremium	Design, Queue, Array +2

Hard (17)

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
0936	Stamping The Sequence	Stack, Greedy, Queue +1
0995	Minimum Number of K Consecutive Bit Flips	Bit Manipulation, Queue, Array +2
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
1825	Finding MK Average	Design, Queue, Data Stream +2
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
2528	Maximize the Minimum Powered City	Greedy, Queue, Array +3
2945	Find Maximum Non-decreasing Array Length	Stack, Queue, Array +4
0683	K Empty SlotsPremium	Binary Indexed Tree, Segment Tree, Queue +5
2534	Time Taken to Cross the DoorPremium	Queue, Array, Simulation
2969	Minimum Number of Coins for Fruits IIPremium	Queue, Array, Dynamic Programming +2

Queue LeetCode Problems: All 43,
With Python Solutions

How Queue problems are solved

When the Queue problem arrives live.

Approach

Approach

Approach

Queue problems by difficulty

Easy (7)

Medium (19)

Hard (17)

Keep exploring

How Queue problems are solved

When the Queue problem arrives live.

Approach

Approach

Approach

Queue problems by difficulty

Easy (7)7

Medium (19)19

Hard (17)17

Keep exploring

Easy (7)

Medium (19)

Hard (17)