From 033ffe88a6ea23d403513b45d7fa43bcacdc7bf4 Mon Sep 17 00:00:00 2001
From: xusiwei1236 <xusiwei1236@163.com>
Date: Fri, 16 Oct 2015 22:09:07 +0800
Subject: [PATCH] new solution of "Binary Tree Level Order Traversal"

---
 .../binaryTreeLevelOrderTraversal.cpp         | 33 +++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/algorithms/binaryTreeLevelOrderTraversal/binaryTreeLevelOrderTraversal.cpp b/algorithms/binaryTreeLevelOrderTraversal/binaryTreeLevelOrderTraversal.cpp
index a1418430d..a5c1225c0 100644
--- a/algorithms/binaryTreeLevelOrderTraversal/binaryTreeLevelOrderTraversal.cpp
+++ b/algorithms/binaryTreeLevelOrderTraversal/binaryTreeLevelOrderTraversal.cpp
@@ -65,12 +65,16 @@ struct TreeNode {
 
 vector<vector<int> > levelOrder1(TreeNode *root);
 vector<vector<int> > levelOrder2(TreeNode *root);
+vector<vector<int> > levelOrder3(TreeNode *root);
 
 
 vector<vector<int> > levelOrder(TreeNode *root) {
     if (random()%2){
         return levelOrder1(root);
     }
+    if (random()%2){
+        return levelOrder3(root);
+    }
     return levelOrder2(root);
 }
 
@@ -149,6 +153,35 @@ vector<vector<int> > levelOrder2(TreeNode *root) {
     return vv;
 }
 
+vector<vector<int> > levelOrder3(TreeNode *root) {
+    vector< vector<int> > vv;
+    if(root == NULL) return vv;
+
+    int level = 0; // current level.
+    TreeNode *last = root; // last node of currrent level.
+    queue<TreeNode*> q;
+
+    q.push(root);
+    vv.push_back(vector<int>());
+    while(!q.empty()) {
+        TreeNode *p = q.front();
+        q.pop();
+
+        vv[level].push_back(p->val);
+        if(p->left ) q.push(p->left);
+        if(p->right) q.push(p->right);
+
+        if(p == last) {
+            level++;
+            last = q.back();
+            vv.push_back(vector<int>()); // new buffer for next row.
+        }
+    }
+    vv.pop_back();
+
+    return vv;
+}
+
 void printTree(TreeNode *root)
 {
     if (root == NULL){