- Difficulty: Medium
- Tags: LeetCode, Medium, Tree, Depth-First Search, Breadth-First Search, Hash Table, leetcode-1443, O(n), DFS, Stack
Problem
Given an undirected tree consisting of n
vertices numbered from 0
to n-1
, which has some apples in their vertices. You spend 1 second to walk over one edge of the tree. Return the minimum time in seconds you have to spend to collect all apples in the tree, starting at vertex 0 and coming back to this vertex.
The edges of the undirected tree are given in the array edges
, where edges[i] = [ai, bi]
means that exists an edge connecting the vertices ai
and bi
. Additionally, there is a boolean array hasApple
, where hasApple[i] = true
means that vertex i
has an apple; otherwise, it does not have any apple.
Example 1:
Input: n = 7, edges = [[0,1],[0,2],[1,4],[1,5],[2,3],[2,6]], hasApple = [false,false,true,false,true,true,false] Output: 8 Explanation: The figure above represents the given tree where red vertices have an apple. One optimal path to collect all apples is shown by the green arrows.
Example 2:
Input: n = 7, edges = [[0,1],[0,2],[1,4],[1,5],[2,3],[2,6]], hasApple = [false,false,true,false,false,true,false] Output: 6 Explanation: The figure above represents the given tree where red vertices have an apple. One optimal path to collect all apples is shown by the green arrows.
Example 3:
Input: n = 7, edges = [[0,1],[0,2],[1,4],[1,5],[2,3],[2,6]], hasApple = [false,false,false,false,false,false,false] Output: 0
Constraints:
1 <= n <= 105
edges.length == n - 1
edges[i].length == 2
0 <= ai < bi <= n - 1
hasApple.length == n