Create 啦啦啦.md

BryceBin · web-flow · commit af09b6f5eb9e · 2018-12-06T21:54:38.000+08:00
diff --git a/2018.12.06-leetcode103/啦啦啦.md b/2018.12.06-leetcode103/啦啦啦.md
@@ -0,0 +1,52 @@
+```java
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode(int x) { val = x; }
+ * }
+ */
+class Solution {
+    public List<List<Integer>> zigzagLevelOrder(TreeNode root) {
+        List<List<Integer>> res = new ArrayList<>();
+        if(root==null)return res;
+        Stack<TreeNode> s1 = new Stack<>();
+        Stack<TreeNode> s2 = new Stack<>();
+        s1.push(root);
+        List<Integer> tmp = new ArrayList<>();
+        while(!s1.empty()){
+            while(!s1.empty()){
+                TreeNode r = s1.pop();
+                tmp.add(r.val);
+                if(r.left!=null){
+                    s2.push(r.left);
+                }
+                if(r.right!=null){
+                    s2.push(r.right);
+                }
+                if(s1.empty()){
+                    res.add(tmp);
+                    tmp = new ArrayList<>();
+                }
+            }
+            while(!s2.empty()){
+                TreeNode r = s2.pop();
+                tmp.add(r.val);
+                if(r.right!=null){
+                    s1.push(r.right);
+                }
+                if(r.left!=null){
+                    s1.push(r.left);
+                }
+                if(s2.empty()){
+                    res.add(tmp);
+                    tmp = new ArrayList<>();
+                }
+            }
+        }
+        return res;
+    }
+}
+```
