Leetcode Problem 1719. Number Of Ways To Reconstruct A Tree

1719. Number Of Ways To Reconstruct A Tree

Leetcode Solutions

Greedy Approach with Degree Sorting and Ancestor Checking

  1. Create a graph g as an adjacency list from the pairs.
  2. Sort the nodes in descending order based on their degree (number of connections).
  3. Initialize an empty set ancestor to keep track of visited nodes.
  4. Iterate over the sorted nodes: a. Find the parent p of the current node x, which is the node with the smallest degree in g[x] that has been visited. b. If p exists, check if g[x] is a subset of g[p] union {p}. If not, return 0. c. If p does not exist and x is not the root (degree is not n-1), return 0. d. If the degrees of p and x are equal, set a flag mul to True, indicating multiple solutions.
  5. After iterating through all nodes, return 1 if mul is False, otherwise return 2.
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DFS Solution with Connected Components and Root Identification

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