剑指 Offer 36. 二叉搜索树与双向链表

Author: geekidentity

src/main/java/com/geekidentity/leetcode/offer/backtracking/Offer36TreeToDoublyList.java

@@ -0,0 +1,53 @@
+package com.geekidentity.leetcode.offer.backtracking;
+
+/**
+ * 搜索与回溯算法
+ * 剑指 Offer 36. 二叉搜索树与双向链表
+ * https://leetcode-cn.com/problems/er-cha-sou-suo-shu-yu-shuang-xiang-lian-biao-lcof/
+ */
+public class Offer36TreeToDoublyList {
+    private Node pre, head;
+
+    public Node treeToDoublyList(Node root) {
+        if (root == null) {
+            return null;
+        }
+        dfs(root);
+        head.left = pre;
+        pre.right = head;
+        return head;
+    }
+
+    private void dfs(Node cur) {
+        if (cur == null) {
+            return;
+        }
+        dfs(cur.left);
+        if (head == null) {
+            head = cur;
+        } else {
+            pre.right = cur;
+        }
+        cur.left = pre;
+        pre = cur;
+        dfs(cur.right);
+    }
+
+    private static class Node {
+        public int val;
+        public Node left;
+        public Node right;
+
+        public Node() {}
+
+        public Node(int _val) {
+            val = _val;
+        }
+
+        public Node(int _val,Node _left,Node _right) {
+            val = _val;
+            left = _left;
+            right = _right;
+        }
+    }
+}