Add solution and test-cases for problem 3249

Author: 0xff-dev

leetcode/3201-3300/3249.Count-the-Number-of-Good-Nodes/1.png

@@ -1,28 +1,43 @@
 # [3249.Count the Number of Good Nodes][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
+There is an **undirected** tree with `n` nodes labeled from `0` to `n - 1`, and rooted at node `0`. You are given a 2D integer array `edges` of length `n - 1`, where `edges[i] = [ai, bi]` indicates that there is an edge between nodes `ai` and `bi` in the tree.
+
+A node is **good** if all the subtrees rooted at its children have the same size.
+
+Return the number of **good** nodes in the given tree.
+
+A **subtree** of `treeName` is a tree consisting of a node in `treeName` and all of its descendants.
 
-**Example 1:**
+**Example 1:**  
+
+![1](./1.png)
 
 ```
-Input: a = "11", b = "1"
-Output: "100"
+Input: edges = [[0,1],[0,2],[1,3],[1,4],[2,5],[2,6]]
+
+Output: 7
 ```
 
-## 题意
-> ...
+**Example 2:**  
 
-## 题解
+![2](./2.png)
 
-### 思路1
-> ...
-Count the Number of Good Nodes
-```go
 ```
+Input: edges = [[0,1],[1,2],[2,3],[3,4],[0,5],[1,6],[2,7],[3,8]]
 
+Output: 6
+```
+
+**Example 3:**  
+
+![3](./3.jpg)
+
+```
+Input: edges = [[0,1],[1,2],[1,3],[1,4],[0,5],[5,6],[6,7],[7,8],[0,9],[9,10],[9,12],[10,11]]
+
+Output: 12
+```
 
 ## 结语
 

leetcode/3201-3300/3249.Count-the-Number-of-Good-Nodes/2.png

@@ -1,5 +1,44 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+func Solution(edges [][]int) int {
+	var ans int
+	n := len(edges) + 1
+	adj := make(map[int][]int)
+	for _, e := range edges {
+		adj[e[0]] = append(adj[e[0]], e[1])
+		adj[e[1]] = append(adj[e[1]], e[0])
+	}
+	size := make([][]int, n)
+	var dfs func(int, int) int
+	dfs = func(root, parent int) int {
+		cnt := 1
+		for _, rel := range adj[root] {
+			if rel == parent {
+				continue
+			}
+			lz := dfs(rel, root)
+			cnt += lz
+			size[root] = append(size[root], lz)
+		}
+		return cnt
+	}
+	dfs(0, -1)
+	for _, ls := range size {
+		if len(ls) == 0 {
+			ans++
+			continue
+		}
+
+		cmp := ls[0]
+		i := 1
+		for ; i < len(ls); i++ {
+			if cmp != ls[i] {
+				break
+			}
+		}
+		if i == len(ls) {
+			ans++
+		}
+	}
+	return ans
 }

leetcode/3201-3300/3249.Count-the-Number-of-Good-Nodes/3.jpg

@@ -10,12 +10,12 @@ func TestSolution(t *testing.T) {
 	//	测试用例
 	cases := []struct {
 		name   string
-		inputs bool
-		expect bool
+		inputs [][]int
+		expect int
 	}{
-		{"TestCase", true, true},
-		{"TestCase", true, true},
-		{"TestCase", false, false},
+		{"TestCase1", [][]int{{0, 1}, {0, 2}, {1, 3}, {1, 4}, {2, 5}, {2, 6}}, 7},
+		{"TestCase2", [][]int{{0, 1}, {1, 2}, {2, 3}, {3, 4}, {0, 5}, {1, 6}, {2, 7}, {3, 8}}, 6},
+		{"TestCase3", [][]int{{0, 1}, {1, 2}, {1, 3}, {1, 4}, {0, 5}, {5, 6}, {6, 7}, {7, 8}, {0, 9}, {9, 10}, {9, 12}, {10, 11}}, 12},
 	}
 
 	//	开始测试
@@ -30,10 +30,10 @@ func TestSolution(t *testing.T) {
 	}
 }
 
-//	压力测试
+// 压力测试
 func BenchmarkSolution(b *testing.B) {
 }
 
-//	使用案列
+// 使用案列
 func ExampleSolution() {
 }