Create 105ConstructBinaryTreefromPreorderandInorderTraversal.cpp

Author: himanshukaushal123

105ConstructBinaryTreefromPreorderandInorderTraversal.cpp

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+class Solution {
+public:
+    TreeNode* buildTree(vector<int>& preorder, vector<int>& inorder) {
+        int rootIdx = 0;
+        return build(preorder, inorder, rootIdx, 0, inorder.size()-1);
+    }
+    
+    TreeNode* build(vector<int>& preorder, vector<int>& inorder, int& rootIdx, int left, int right) {
+        if (left > right) return NULL;
+        int pivot = left;  // find the root from inorder
+        while(inorder[pivot] != preorder[rootIdx]) pivot++;
+        
+        rootIdx++;
+        TreeNode* newNode = new TreeNode(inorder[pivot]);
+        newNode->left = build(preorder, inorder, rootIdx, left, pivot-1);
+        newNode->right = build(preorder, inorder, rootIdx, pivot+1, right);
+        return newNode;
+    }
+};