add sol

leetcode/543.DiameterofBinaryTree/diameterofBinaryTree.go

@@ -0,0 +1,40 @@
+// https://leetcode.com/problems/diameter-of-binary-tree
+
+package main
+
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+
+type TreeNode struct {
+	Val   int
+	Left  *TreeNode
+	Right *TreeNode
+}
+
+func diameterOfBinaryTree(root *TreeNode) int {
+	ans := 0
+	var dfs func(root *TreeNode) int
+	dfs = func(root *TreeNode) int {
+		if root == nil {
+			return 0
+		}
+		left, right := dfs(root.Left), dfs(root.Right)
+		ans = max(ans, left+right)
+		return 1 + max(left, right)
+	}
+	dfs(root)
+	return ans
+}
+
+func max(a, b int) int {
+	if a > b {
+		return a
+	}
+	return b
+}