feat: add golang solution for lcof problems 26-28

Author: hzliangbin

lcof/面试题26. 树的子结构/README.md

@@ -161,7 +161,32 @@ var isSubStructure = function(A, B) {
 };
 ```
 
+### Go
+
+```go
+func isSubStructure(A *TreeNode, B *TreeNode) bool {
+    //约定空树不是任意一个树的子结构
+    if A == nil || B == nil {
+        return false
+    }
+    return helper(A,B) || isSubStructure(A.Left,B) || isSubStructure(A.Right,B) 
+}
+
+func helper(a *TreeNode, b *TreeNode) bool {
+    if b ==  nil {
+        return true
+    }
+    if a == nil {
+        return false
+    }
+    return a.Val == b.Val && helper(a.Left, b.Left) && helper(a.Right, b.Right)
+}
+```
+
+
+
 ### ...
+
 ```
 
 ```

lcof/面试题26. 树的子结构/Solution.go

@@ -0,0 +1,17 @@
+func isSubStructure(A *TreeNode, B *TreeNode) bool {
+    //约定空树不是任意一个树的子结构
+    if A == nil || B == nil {
+        return false
+    }
+    return helper(A,B) || isSubStructure(A.Left,B) || isSubStructure(A.Right,B) 
+}
+
+func helper(a *TreeNode, b *TreeNode) bool {
+    if b ==  nil {
+        return true
+    }
+    if a == nil {
+        return false
+    }
+    return a.Val == b.Val && helper(a.Left, b.Left) && helper(a.Right, b.Right)
+}

lcof/面试题27. 二叉树的镜像/README.md

@@ -107,7 +107,24 @@ var mirrorTree = function(root) {
 };
 ```
 
+### Go
+
+```go
+func mirrorTree(root *TreeNode) *TreeNode {
+    if root == nil {
+        return root
+    }
+    root.Left, root.Right = root.Right, root.Left
+    root.Left = mirrorTree(root.Left)
+    root.Right = mirrorTree(root.Right)
+    return root
+}
+```
+
+
+
 ### ...
+
 ```
 
 ```

lcof/面试题27. 二叉树的镜像/Solution.go

@@ -0,0 +1,9 @@
+func mirrorTree(root *TreeNode) *TreeNode {
+    if root == nil {
+        return root
+    }
+    root.Left, root.Right = root.Right, root.Left
+    root.Left = mirrorTree(root.Left)
+    root.Right = mirrorTree(root.Right)
+    return root
+}

lcof/面试题28. 对称的二叉树/README.md

@@ -120,7 +120,34 @@ var isSymmetric = function(root) {
 };
 ```
 
+### Go
+
+```go
+func isSymmetric(root *TreeNode) bool {
+    if root == nil {
+        return true
+    }
+    return isSymme(root.Left, root.Right)
+}
+
+func isSymme(a *TreeNode, b *TreeNode) bool {
+    if a == nil && b == nil {
+        return true
+    }
+    if a == nil || b ==nil {
+        return false
+    }
+    if a.Val != b.Val {
+        return false
+    }
+    return isSymme(a.Left,b.Right) && isSymme(a.Right, b.Left)
+}
+```
+
+
+
 ### ...
+
 ```
 
 ```

lcof/面试题28. 对称的二叉树/Solution.go

@@ -0,0 +1,19 @@
+func isSymmetric(root *TreeNode) bool {
+    if root == nil {
+        return true
+    }
+    return isSymme(root.Left, root.Right)
+}
+
+func isSymme(a *TreeNode, b *TreeNode) bool {
+    if a == nil && b == nil {
+        return true
+    }
+    if a == nil || b ==nil {
+        return false
+    }
+    if a.Val != b.Val {
+        return false
+    }
+    return isSymme(a.Left,b.Right) && isSymme(a.Right, b.Left)
+}