Merge pull request #855 from 0xff-dev/310

Add solution and test-cases for problem 310

Author: 6boris

leetcode/301-400/0310.Minimum-Height-Trees/README.md

@@ -1,28 +1,32 @@
 # [310.Minimum Height Trees][title]
 
-> [!WARNING|style:flat]
-> This question is temporarily unanswered if you have good ideas. Welcome to [Create Pull Request PR](https://github.com/kylesliu/awesome-golang-algorithm)
-
 ## Description
+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 `0` to `n - 1`, and an array of `n - 1` `edges` where `edges[i] = [ai, bi]` indicates that there is an undirected edge between the two nodes `ai` and `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.
 
-**Example 1:**
+**Example 1:**  
+
+![1](./e1.jpeg)
 
 ```
-Input: a = "11", b = "1"
-Output: "100"
+Input: n = 4, edges = [[1,0],[1,2],[1,3]]
+Output: [1]
+Explanation: As shown, the height of the tree is 1 when the root is the node with label 1 which is the only MHT.
 ```
 
-## 题意
-> ...
+**Example 2:**  
 
-## 题解
+![2](./e2.jpeg)
 
-### 思路1
-> ...
-Minimum Height Trees
-```go
 ```
-
+Input: n = 6, edges = [[3,0],[3,1],[3,2],[3,4],[5,4]]
+Output: [3,4]
+```
 
 ## 结语
 

leetcode/301-400/0310.Minimum-Height-Trees/Solution.go

@@ -1,5 +1,39 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+func Solution(n int, edges [][]int) []int {
+	if n == 1 {
+		return []int{0}
+	}
+	adj := make([]map[int]struct{}, n)
+	for i := 0; i < n; i++ {
+		adj[i] = make(map[int]struct{})
+	}
+	for _, edge := range edges {
+		a, b := edge[0], edge[1]
+		adj[a][b] = struct{}{}
+		adj[b][a] = struct{}{}
+	}
+	l := []int{}
+	for i := 0; i < n; i++ {
+		if len(adj[i]) == 1 {
+			l = append(l, i)
+		}
+	}
+	r := n
+	for r > 2 {
+		r -= len(l)
+		nl := []int{}
+		for _, lf := range l {
+			var nei int
+			for n := range adj[lf] {
+				nei = n
+			}
+			delete(adj[nei], lf)
+			if len(adj[nei]) == 1 {
+				nl = append(nl, nei)
+			}
+		}
+		l = nl
+	}
+	return l
 }

leetcode/301-400/0310.Minimum-Height-Trees/Solution_test.go

@@ -10,30 +10,34 @@ func TestSolution(t *testing.T) {
 	//	测试用例
 	cases := []struct {
 		name   string
-		inputs bool
-		expect bool
+		n      int
+		edges  [][]int
+		expect []int
 	}{
-		{"TestCase", true, true},
-		{"TestCase", true, true},
-		{"TestCase", false, false},
+		{"TestCase1", 4, [][]int{
+			{1, 0}, {1, 2}, {1, 3},
+		}, []int{1}},
+		{"TestCase2", 6, [][]int{
+			{3, 0}, {3, 1}, {3, 2}, {3, 4}, {5, 4},
+		}, []int{3, 4}},
 	}
 
 	//	开始测试
 	for i, c := range cases {
 		t.Run(c.name+" "+strconv.Itoa(i), func(t *testing.T) {
-			got := Solution(c.inputs)
+			got := Solution(c.n, c.edges)
 			if !reflect.DeepEqual(got, c.expect) {
-				t.Fatalf("expected: %v, but got: %v, with inputs: %v",
-					c.expect, got, c.inputs)
+				t.Fatalf("expected: %v, but got: %v, with inputs: %v %v",
+					c.expect, got, c.n, c.edges)
 			}
 		})
 	}
 }
 
-//	压力测试
+// 压力测试
 func BenchmarkSolution(b *testing.B) {
 }
 
-//	使用案列
+// 使用案列
 func ExampleSolution() {
 }