Binary Search Tree LeetCode Problems: 40 Python Solutions

1 pattern

How Binary Search Tree problems are solved

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

Tree TraversalChoose the order — preorder, inorder, postorder, level — and the problem solves itself.

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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...

GPT-6.1 TerraClear chat

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...

GPT-6.1 TerraClear chat

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

Binary Search Tree problems by difficulty

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

Easy (10)

Easy problems
No.	Problem	Topics
0108	Convert Sorted Array to Binary Search Tree	Tree, Binary Search Tree, Array +2
0501	Find Mode in Binary Search Tree	Tree, Depth-First Search, Binary Search Tree +1
0530	Minimum Absolute Difference in BST	Tree, Depth-First Search, Breadth-First Search +2
0653	Two Sum IV - Input is a BST	Tree, Depth-First Search, Breadth-First Search +4
0700	Search in a Binary Search Tree	Tree, Binary Search Tree, Binary Tree
0703	Kth Largest Element in a Stream	Tree, Design, Binary Search Tree +3
0783	Minimum Distance Between BST Nodes	Tree, Depth-First Search, Breadth-First Search +2
0897	Increasing Order Search Tree	Stack, Tree, Depth-First Search +2
0938	Range Sum of BST	Tree, Depth-First Search, Binary Search Tree +1
0270	Closest Binary Search Tree ValuePremium	Tree, Depth-First Search, Binary Search Tree +2

Medium (27)

Medium problems
No.	Problem	Topics
0095	Unique Binary Search Trees II	Tree, Binary Search Tree, Dynamic Programming +2
0096	Unique Binary Search Trees	Tree, Binary Search Tree, Math +2
0098	Validate Binary Search Tree	Tree, Depth-First Search, Binary Search Tree +1
0099	Recover Binary Search Tree	Tree, Depth-First Search, Binary Search Tree +1
0109	Convert Sorted List to Binary Search Tree	Tree, Binary Search Tree, Linked List +2
0173	Binary Search Tree Iterator	Stack, Tree, Design +3
0230	Kth Smallest Element in a BST	Tree, Depth-First Search, Binary Search Tree +1
0235	Lowest Common Ancestor of a Binary Search Tree	Tree, Depth-First Search, Binary Search Tree +1
0449	Serialize and Deserialize BST	Tree, Depth-First Search, Breadth-First Search +4
0450	Delete Node in a BST	Tree, Binary Search Tree, Binary Tree
0538	Convert BST to Greater Tree	Tree, Depth-First Search, Binary Search Tree +1
0669	Trim a Binary Search Tree	Tree, Depth-First Search, Binary Search Tree +1
0701	Insert into a Binary Search Tree	Tree, Binary Search Tree, Binary Tree
1008	Construct Binary Search Tree from Preorder Traversal	Stack, Tree, Binary Search Tree +3
1038	Binary Search Tree to Greater Sum Tree	Tree, Depth-First Search, Binary Search Tree +1
1305	All Elements in Two Binary Search Trees	Tree, Depth-First Search, Binary Search Tree +2
1382	Balance a Binary Search Tree	Greedy, Tree, Depth-First Search +3
2476	Closest Nodes Queries in a Binary Search Tree	Tree, Depth-First Search, Binary Search Tree +3
0255	Verify Preorder Sequence in Binary Search TreePremium	Stack, Tree, Binary Search Tree +4
0285	Inorder Successor in BSTPremium	Tree, Depth-First Search, Binary Search Tree +1
0333	Largest BST SubtreePremium	Tree, Depth-First Search, Binary Search Tree +2
0426	Convert Binary Search Tree to Sorted Doubly Linked ListPremium	Stack, Tree, Depth-First Search +4
0510	Inorder Successor in BST IIPremium	Tree, Binary Search Tree, Binary Tree
0776	Split BSTPremium	Tree, Binary Search Tree, Recursion +1
1214	Two Sum BSTsPremium	Stack, Tree, Depth-First Search +4
1586	Binary Search Tree Iterator IIPremium	Stack, Tree, Design +3
1902	Depth of BST Given Insertion OrderPremium	Tree, Binary Search Tree, Array +2

Hard (3)

Hard problems
No.	Problem	Topics
1373	Maximum Sum BST in Binary Tree	Tree, Depth-First Search, Binary Search Tree +2
1569	Number of Ways to Reorder Array to Get Same BST	Tree, Union Find, Binary Search Tree +7
0272	Closest Binary Search Tree Value IIPremium	Stack, Tree, Depth-First Search +4

Binary Search Tree LeetCode Problems: All 40,
With Python Solutions

How Binary Search Tree problems are solved

When the Binary Search Tree problem arrives live.

Approach

Approach

Approach

Binary Search Tree problems by difficulty

Easy (10)

Medium (27)

Hard (3)

Keep exploring

How Binary Search Tree problems are solved

When the Binary Search Tree problem arrives live.

Approach

Approach

Approach

Binary Search Tree problems by difficulty

Easy (10)10

Medium (27)27

Hard (3)3

Keep exploring

Easy (10)

Medium (27)

Hard (3)