Doubly-Linked List LeetCode Problems: 10 Python Solutions

1 pattern

How Doubly-Linked List problems are solved

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

Linked ListRewire pointers in place, with a dummy head and a saved next to keep it safe.

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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+

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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+

Doubly-Linked List problems by difficulty

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

Medium (6)

Medium problems
No.	Problem	Topics
0146	LRU Cache	Design, Hash Table, Linked List +1
0430	Flatten a Multilevel Doubly Linked List	Depth-First Search, Linked List, Doubly-Linked List
1472	Design Browser History	Stack, Design, Array +3
1797	Design Authentication Manager	Design, Hash Table, Linked List +1
0426	Convert Binary Search Tree to Sorted Doubly Linked ListPremium	Stack, Tree, Depth-First Search +4
1756	Design Most Recently Used QueuePremium	Design, Array, Linked List +3

Hard (4)

Hard problems
No.	Problem	Topics
0432	All O`one Data Structure	Design, Hash Table, Linked List +1
0460	LFU Cache	Design, Hash Table, Linked List +1
2296	Design a Text Editor	Stack, Design, Linked List +3
0716	Max StackPremium	Stack, Design, Linked List +2

Doubly-Linked List LeetCode Problems: All 10,
With Python Solutions

How Doubly-Linked List problems are solved

When the Doubly-Linked List problem arrives live.

Approach

Approach

Approach

Doubly-Linked List problems by difficulty

Medium (6)

Hard (4)

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How Doubly-Linked List problems are solved

When the Doubly-Linked List problem arrives live.

Approach

Approach

Approach

Doubly-Linked List problems by difficulty

Medium (6)6

Hard (4)4

Keep exploring

Medium (6)

Hard (4)