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Author: kedebug

ConstructBinaryTreefromInorderandPostorderTraversal/ConstructBinaryTreefromInorderandPostorderTraversal.cpp

@@ -0,0 +1,49 @@
+/**
+ * Definition for binary tree
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
+ * };
+ */
+class Solution {
+public:
+    TreeNode *buildTree(vector<int>& inorder, vector<int>& postorder) {
+        // Start typing your C/C++ solution below
+        // DO NOT write int main() function
+        
+        int size = inorder.size();
+        if (size == 0) return NULL;
+        
+        TreeNode *root = new TreeNode(0);
+        build(root, size, inorder, 0, postorder, 0);
+        return root;
+    }
+    
+    void build(TreeNode *root, int size, vector<int>& inorder, int inLeft, vector<int>& postorder, int postLeft) {
+        assert(size > 0);
+        
+        int pivot = postorder[postLeft+size-1];
+        root->val = pivot;
+        
+        if (size == 1) return;
+        
+        int sizeleft = 0;
+        for (int i = 0; i < size; i++) {
+            if (inorder[inLeft+i] == pivot)
+                break;
+            sizeleft += 1;
+        }
+        
+        if (sizeleft > 0) {
+            root->left = new TreeNode(0);
+            build(root->left, sizeleft, inorder, inLeft, postorder, postLeft);
+        }
+        int sizeright = size - sizeleft - 1;
+        if (sizeright > 0) {
+            root->right = new TreeNode(0);
+            build(root->right, sizeright, inorder, inLeft + sizeleft + 1, postorder, postLeft + sizeleft);
+        }
+    }
+};

ConstructBinaryTreefromPreorderandInorderTraversal/ConstructBinaryTreefromPreorderandInorderTraversal.cpp

@@ -0,0 +1,45 @@
+/**
+ * Definition for binary tree
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
+ * };
+ */
+class Solution {
+public:
+    TreeNode *buildTree(vector<int>& preorder, vector<int>& inorder) {
+        // Start typing your C/C++ solution below
+        // DO NOT write int main() function
+        
+        if (preorder.empty()) return NULL;
+        
+        TreeNode *root = new TreeNode(0);
+        build(root, preorder.size(), preorder, 0, inorder, 0);
+        return root;
+    }
+    
+    void build(TreeNode *root, int size, vector<int>& preorder, int preLeft, vector<int>& inorder, int inLeft) {
+        if (size == 1) {
+            root->val = preorder[preLeft];
+            return ;
+        }
+        int sizeLeft = 0;
+        for (int i = 0; i < size; i++) {
+            if (preorder[preLeft] == inorder[i+inLeft])
+                break;
+            sizeLeft += 1;
+        }
+        root->val = preorder[preLeft];
+        if (sizeLeft > 0) {
+            root->left = new TreeNode(0);
+            build(root->left, sizeLeft, preorder, preLeft + 1, inorder, inLeft);
+        }
+        int sizeRight = size - sizeLeft - 1;
+        if (sizeRight > 0) {
+            root->right = new TreeNode(0);
+            build(root->right, sizeRight, preorder, preLeft + sizeLeft + 1, inorder, inLeft + sizeLeft + 1);
+        }
+    }
+};