1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46

// @Title: 最小高度树 (Minimum Height Trees)
// @Author: 15816537946@163.com
// @Date: 2022-04-06 11:28:35
// @Runtime: 64 ms
// @Memory: 11.1 MB
func findMinHeightTrees(n int, edges [][]int) []int {
    if n == 1 {
        return []int{0}
    }

    g := make([][]int, n)
    for _, e := range edges {
        x, y := e[0], e[1]
        g[x] = append(g[x], y)
        g[y] = append(g[y], x)
    }

    parents := make([]int, n)
    maxDepth, node := 0, -1
    var dfs func(int, int, int)
    dfs = func(x, pa, depth int) {
        if depth > maxDepth {
            maxDepth, node = depth, x
        }
        parents[x] = pa
        for _, y := range g[x] {
            if y != pa {
                dfs(y, x, depth+1)
            }
        }
    }
    dfs(0, -1, 1)
    maxDepth = 0
    dfs(node, -1, 1)

    path := []int{}
    for node != -1 {
        path = append(path, node)
        node = parents[node]
    }
    m := len(path)
    if m%2 == 0 {
        return []int{path[m/2-1], path[m/2]}
    }
    return []int{path[m/2]}
}