Practice-Leetcode/PreorderInorderTree.cpp at master · adilhamid/Practice-Leetcode · GitHub

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/**
 * Definition for a binary tree node.
 * 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) {
        if(preorder.empty() || inorder.empty()) return NULL;

        stack<TreeNode*> Tree;
        TreeNode* root, *temp;

        root = new TreeNode(preorder.front());
        preorder.erase(preorder.begin());
        Tree.push(root);

        while(!preorder.empty()){

            if(inorder.front() == Tree.top()->val){

                temp = Tree.top();
                Tree.pop();
                inorder.erase(inorder.begin());

                if(inorder.empty()) break;

                if(!Tree.empty() && inorder.front() == Tree.top()->val)
                    continue;

                temp->right = new TreeNode(preorder.front());
                 preorder.erase(preorder.begin());
                Tree.push(temp->right);

            }

            else{
                temp = new TreeNode(preorder.front());
                preorder.erase(preorder.begin());
                Tree.top()->left = temp;
                Tree.push(temp);

            }


        }
         return root;

    }
};