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Author: assassint2017

Construct Binary Tree from Inorder and Postorder Traversal/Construct_Binary_Tree_from_Inorder_and_Postorder_Traversal.cpp

@@ -0,0 +1,45 @@
+// 和上一道题目的解题思路是一样的
+// 16ms 54.05%
+
+/**
+ * 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<algorithm>
+using namespace std;
+
+class Solution {
+public:
+    TreeNode* buildTree(vector<int>& inorder, vector<int>& postorder) 
+    {
+        return helper(0, postorder.size() - 1, 0, inorder.size() - 1, postorder, inorder);
+    }
+
+    TreeNode* helper(int postLeft, int postRight, int inLeft, int inRight, vector<int>& postorder, vector<int>& inorder)
+    {   
+        if (postLeft > postRight)
+            return 0;
+        else if (postLeft == postRight)
+            return new TreeNode(postorder[postLeft]);
+        else
+        {
+            int rootValue = postorder[postRight];
+        
+            vector<int>::iterator iter = find(inorder.begin() + inLeft, inorder.begin() + inRight + 1, rootValue);
+            int rootIndex = iter - inorder.begin();
+
+            TreeNode *root = new TreeNode(rootValue);
+            root->left = helper(postLeft, postLeft + rootIndex - inLeft - 1, inLeft, rootIndex - 1, postorder, inorder);
+            root->right = helper(postLeft + rootIndex - inLeft, postRight - 1, rootIndex + 1, inRight, postorder, inorder);
+
+            return root;
+        }
+    }
+};

Construct Binary Tree from Inorder and Postorder Traversal/Construct_Binary_Tree_from_Inorder_and_Postorder_Traversal.py

@@ -0,0 +1,33 @@
+# 160ms 81.93%
+
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, x):
+#         self.val = x
+#         self.left = None
+#         self.right = None
+
+class Solution:
+    def buildTree(self, inorder, postorder):
+        """
+        :type inorder: List[int]
+        :type postorder: List[int]
+        :rtype: TreeNode
+        """
+        return self.helper(0, len(postorder) - 1, 0, len(inorder) - 1, postorder, inorder)
+        
+    def helper(self, postLeft, postRight, inLeft, inRight, postorder, inorder):
+        if postLeft > postRight:
+            return None
+        elif postLeft == postRight:
+            return TreeNode(postorder[postRight])
+        else:
+            rootValue = postorder[postRight]
+            rootIndex = inorder.index(rootValue)
+
+            root = TreeNode(rootValue)
+            root.left = self.helper(postLeft, postLeft + rootIndex - inLeft - 1, inLeft, rootIndex - 1, postorder, inorder)
+            root.right = self.helper(postLeft + rootIndex - inLeft, postRight - 1, rootIndex + 1, inRight, postorder, inorder)
+
+            return root
+