Given preorder and inorder traversal of a tree, construct the binary tree.
Note:
You may assume that duplicates do not exist in the tree.
TreeNode* build(vector<int> &preorder,int left1,int right1,vector<int> &inorder,int left2,int right2) { if(right1-left1 != right2-left2)return NULL; if(right1>=preorder.size() || right2>=inorder.size())return NULL; if(left1==right1 && left2==right2) { TreeNode* root = new TreeNode(preorder[left1]); return root; }else if(left1<right1 && left2<right2) { TreeNode* root = new TreeNode(preorder[left1]); int i; for(i = left2; i <= right2; i++) if(inorder[i] == preorder[left1])break; if(i>right2)return NULL; root->left = build(preorder,left1+1,left1+i-left2,inorder,left2,i-1); root->right = build(preorder,left1+i-left2+1,right1,inorder,i+1,right2); return root; }else return NULL; } TreeNode *buildTree(vector<int> &preorder, vector<int> &inorder) { // Note: The Solution object is instantiated only once. return build(preorder,0,preorder.size()-1,inorder,0,inorder.size()-1); }