add one more

Author: anson627

BinaryTreeLevelOrderTraversalII/BinaryTreeLevelOrderTraversalII.cpp

@@ -5,11 +5,11 @@
 //
 // For example:
 // Given binary tree {3,9,20,#,#,15,7},
-//    3
-//   / \
-//  9  20
-//    /  \
-//   15   7
+// "    3      "
+// "   / \     "
+// "  9  20    "
+// "    /  \   "
+// "   15   7  "
 // return its bottom-up level order traversal as:
 // [
 //   [15,7]
@@ -20,6 +20,8 @@
 
 #include <iostream>
 #include <vector>
+#include <stack>
+
 using namespace std;
 
 /**
@@ -34,34 +36,75 @@ struct TreeNode {
 
 class Solution {
 public:
-    vector<vector<int> > levelOrderBottom(TreeNode *root) {
+    vector<vector<int> > levelOrderBottom(TreeNode *root)
+    {
+        //return levelOrderBottom1(root);
+        return levelOrderBottom2(root);
+    }
+
+    vector<vector<int> > levelOrderBottom1(TreeNode *root)
+    {
         vector<vector<int> > res;
         vector<int> row;
-        for (int level = maxHeight(root); level >= 1; level--) {
+        for (int level = maxHeight(root); level >= 1; level--)
+        {
             row.clear();
             levelOrderBottomHelper(root, level, row);
             res.push_back(row);
         }
         return res;
-
     }
 
-    int maxHeight(TreeNode *node) {
+    int maxHeight(TreeNode *node)
+    {
         if(NULL == node) return 0;
         return 1 + max(maxHeight(node->left), maxHeight(node->right));
     };
 
-    void levelOrderBottomHelper(TreeNode *node, int level, vector<int> &row) {
+    void levelOrderBottomHelper(TreeNode *node, int level, vector<int> &row)
+    {
         if (level == 0 || node == NULL) return;
-        if (level == 1) {
+        if (level == 1)
+        {
             row.push_back(node->val);
             return;
         }
         levelOrderBottomHelper(node->left, level-1, row);
         levelOrderBottomHelper(node->right, level-1, row);
     }
+
+    vector<vector<int> > levelOrderBottom2(TreeNode *root)
+    {
+        vector<vector<int> > res;
+        if (!root) return res;
+
+        stack<vector<TreeNode*> > stk;
+        stk.push(vector<TreeNode*>(1, root));
+        while(true)
+        {
+            vector<TreeNode*> row;
+            for (vector<TreeNode*>::iterator it = stk.top().begin(); it != stk.top().end(); ++it)
+            {
+                if ((*it)->left) row.push_back((*it)->left);
+                if ((*it)->right) row.push_back((*it)->right);
+            }
+            if (row.empty()) break;
+            stk.push(row);
+        }
+
+        while (!stk.empty())
+        {
+            vector<int> row;
+            for (vector<TreeNode*>::iterator it = stk.top().begin(); it != stk.top().end(); ++it)
+                row.push_back((*it)->val);
+            res.push_back(row);
+            stk.pop();
+        }
+        return res;
+    }
 };
 
-int main() {
+int main()
+{
     return 0;
 }