Visualizations

TreeNode, ListNode, and GraphNode render as diagrams in Jupyter and clean ASCII in the terminal.

The data structure classes from leetcode_py convert between LeetCode’s array format and live objects, and render themselves so you can look at what your code is doing.

from leetcode_py import GraphNode, ListNode, TreeNode

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Array format, live objects

root = TreeNode.from_list([3, 9, 20, None, None, 15, 7])
root.to_list()          # [3, 9, 20, None, None, 15, 7]

head = ListNode.from_list([1, 2, 3])
head.to_list()          # [1, 2, 3]

graph = GraphNode.from_adjacency_list([[2, 4], [1, 3], [2, 4], [1, 3]])
GraphNode.to_adjacency_list(graph)  # [[2, 4], [1, 3], [2, 4], [1, 3]]

Cyclic lists are safe: traversal detects cycles instead of hanging, in both directions.

Each class carries a few extras beyond conversion and rendering:

• TreeNode.find_node(value) returns the first node with that value.
• GraphNode.is_clone(other) checks deep equality between a graph and its copy, the shape clone-graph problems ask for.
• All three are generic: TreeNode[int], ListNode[str], and so on.
• from leetcode_py.data_structures import DictTree gives a dict-backed tree that renders with box-drawing characters in the terminal and Graphviz in Jupyter, which suits Trie implementations.

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In Jupyter: diagrams

As the last expression of a cell, these objects render as Graphviz SVG diagrams. TreeNode lays out top-to-bottom; ListNode goes left-to-right with rounded boxes. A cyclic list draws the back-edge in red, dashed, and labeled cycle.

head = ListNode.from_list([1, 2, 3])
head.next.next.next = head.next   # cycle: 3 -> 2
head                              # renders the diagram, cycle included

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In the terminal: ASCII

print() falls back to clean text: an indented tree, an arrow chain for lists (cycles shown as ... (cycle back to 2)), and a formatted adjacency dict for graphs.

print(root)
# 3
# ├── 9
# └── 20
#     ├── 15
#     └── 7

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Requirements

Diagram rendering needs the system Graphviz binary (see Installation). If it is missing, the objects fall back to the ASCII form, so you get readable output either way.