class Solution { private: TreeNode* generateTree(int postStart, int postEnd, int inStart, int inEnd, vector<int>& postorder, vector<int>& inorder) { if(postStart > postEnd || inStart > inEnd) return NULL; TreeNode* root = new TreeNode(postorder[postEnd]); int inIndex = 0; for(int i = inStart; i <= inEnd; i++) { if(inorder[i] == postorder[postEnd]){ inIndex = i; break; } } root->left = generateTree(postStart, postStart+inIndex-inStart-1, inStart, inIndex-1, postorder, inorder); root->right = generateTree(postEnd-inEnd+inIndex, postEnd-1, inIndex+1, inEnd, postorder, inorder); return root; } public: TreeNode* buildTree(vector<int>& inorder, vector<int>& postorder) { return generateTree(0, postorder.size()-1, 0, inorder.size()-1, postorder, inorder); } };
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