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 109 + 7
.
Note: Ignore all edges not in the path from node 1 to x
.
Example 1:
Input: edges = [[1,2]]
Output: 1
Explanation:
1 → 2
).Example 2:
Input: edges = [[1,2],[1,3],[3,4],[3,5]]
Output: 2
Explanation:
1 → 3
and 3 → 4
).
Constraints:
2 <= n <= 105
edges.length == n - 1
edges[i] == [ui, vi]
1 <= ui, vi <= n
edges
represents a valid tree.