Update 0101

leetcode/0101.Symmetric-Tree/101. Symmetric Tree.go

@@ -16,19 +16,51 @@ type TreeNode = structures.TreeNode
  * }
  */
 
+// 解法一 dfs
 func isSymmetric(root *TreeNode) bool {
-	var dfs func(rootLeft, rootRight *TreeNode) bool
-	dfs = func(rootLeft, rootRight *TreeNode) bool {
-		if rootLeft == nil && rootRight == nil {
-			return true
-		}
-		if rootLeft == nil || rootRight == nil {
-			return false
-		}
-		if rootLeft.Val != rootRight.Val {
-			return false
-		}
-		return dfs(rootLeft.Left, rootRight.Right) && dfs(rootLeft.Right, rootRight.Left)
-	}
 	return root == nil || dfs(root.Left, root.Right)
 }
+
+func dfs(rootLeft, rootRight *TreeNode) bool {
+	if rootLeft == nil && rootRight == nil {
+		return true
+	}
+	if rootLeft == nil || rootRight == nil {
+		return false
+	}
+	if rootLeft.Val != rootRight.Val {
+		return false
+	}
+	return dfs(rootLeft.Left, rootRight.Right) && dfs(rootLeft.Right, rootRight.Left)
+}
+
+// 解法二
+func isSymmetric1(root *TreeNode) bool {
+	if root == nil {
+		return true
+	}
+	return isSameTree(invertTree(root.Left), root.Right)
+}
+
+func isSameTree(p *TreeNode, q *TreeNode) bool {
+	if p == nil && q == nil {
+		return true
+	} else if p != nil && q != nil {
+		if p.Val != q.Val {
+			return false
+		}
+		return isSameTree(p.Left, q.Left) && isSameTree(p.Right, q.Right)
+	} else {
+		return false
+	}
+}
+
+func invertTree(root *TreeNode) *TreeNode {
+	if root == nil {
+		return nil
+	}
+	invertTree(root.Left)
+	invertTree(root.Right)
+	root.Left, root.Right = root.Right, root.Left
+	return root
+}