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Author: assassint2017

Binary Tree Preorder Traversal/Binary_Tree_Preorder_Traversal.cpp

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+// 递归的过于简单了，这里就直接使用堆栈来做了
+// 0ms 100%
+
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
+ * };
+ */
+
+#include<vector>
+#include<stack>
+using namespace std;
+
+class Solution {
+public:
+    vector<int> preorderTraversal(TreeNode* root) {
+        vector<int> values;
+        stack<TreeNode*> treeStack;
+        if (!root)        
+            return values;
+        
+        while (root || !treeStack.empty())
+        {
+            while (root)
+            {
+                values.push_back(root->val);
+                treeStack.push(root);
+                root = root->left;
+            }
+
+            if (!treeStack.empty())
+            {
+                root = treeStack.top();
+                treeStack.pop();
+
+                root = root->right;
+            }
+        }
+        return values;
+    }
+};

Binary Tree Preorder Traversal/Binary_Tree_Preorder_Traversal.py

@@ -0,0 +1,29 @@
+# 52ms 99.00%
+
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, x):
+#         self.val = x
+#         self.left = None
+#         self.right = None
+
+class Solution:
+    def preorderTraversal(self, root):
+        """
+        :type root: TreeNode
+        :rtype: List[int]
+        """
+        values = []
+        treeStack = []
+
+        if (root is None):
+            return values
+        while root or len(treeStack) > 0:
+            while root:
+                values.append(root.val)
+                treeStack.append(root)
+                root = root.left
+            if len(treeStack) > 0:
+                root = treeStack.pop()
+                root = root.right
+        return values