Number of Ways to Assign Edge Weights I
There is an undirected tree with n nodes labeled from 1 to n, rooted at node 1.
There is an undirected tree with n nodes labeled from 1 to n, rooted at node 1. The tree is represented by a 2D integer array edges of length n - 1, where edges[i] = [ui, vi] indicates that there is an edge between nodes ui and vi.
Initially, all edges have a weight of 0. You must assign each edge a weight of either 1 or 2.
The cost of a path between any two nodes u and v is the total weight of all edges in the path connecting them.
Select any one node x at the maximum depth. Return the number of ways to assign edge weights in the path from node 1 to x such that its total cost is odd.
Since the answer may be large, return it modulo 10^9 + 7.
Note: Ignore all edges not in the path from node 1 to x.
Example 1
Input: edges = [[1,2]]
Output: 1
Example 2
Input: edges = [[1,2],[1,3],[3,4],[3,5]]
Output: 2
Constraints
- 2 <= n <= 10^5
- edges.length == n - 1
- edges[i] == [ui, vi]
- 1 <= ui, vi <= n
- edges represents a valid tree.
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