A tree is an undirected graph in which any two vertices are connected by exactly one path. In other words, any connected graph without simple cycles is a tree.
Given a tree of
n nodes labelled from
n - 1, and an array of
n - 1
edges[i] = [ai, bi] indicates that there is an undirected edge between the two nodes
bi in the tree, you can choose any node of the tree as the root. When you select a node
x as the root, the result tree has height
h. Among all possible rooted trees, those with minimum height (i.e.
min(h)) are called minimum height trees (MHTs).
Return a list of all MHTs' root labels. You can return the answer in any order.
The height of a rooted tree is the number of edges on the longest downward path between the root and a leaf.
Input: n = 4, edges = [[1,0],[1,2],[1,3]] Output:  Explanation: As shown, the height of the tree is 1 when the root is the node with label 1 which is the only MHT.
Input: n = 6, edges = [[3,0],[3,1],[3,2],[3,4],[5,4]] Output: [3,4]
Input: n = 1, edges =  Output: 
Input: n = 2, edges = [[0,1]] Output: [0,1]
1 <= n <= 2 * 104
edges.length == n - 1
0 <= ai, bi < n
ai != bi
(ai, bi)are distinct.