从前序与中序遍历序列中构造二叉树

力扣——题目

运用迭代的方法去求解

class Solution {
public:
    TreeNode* buildTree(vector& preorder, vector& inorder) 
    {
        int prvei=0;
        int begin=0;
        int end=inorder.size()-1;
        return _buildTree(preorder,inorder,prvei,0,end);
    }
private:
       TreeNode* _buildTree(vector& preorder, vector& inorder,int& prvei,int begin,int end)
       {
           if(begin>end)
                return nullptr;
           TreeNode*root=new TreeNode(preorder[prvei]);
           int rooti=begin;
           while(rooti<=end)
           {
               if(inorder[rooti]==preorder[prvei])
               {
                   break;
               }
               else
                rooti++;
           }
           prvei++;
          root->left= _buildTree(preorder,inorder,prvei,begin,rooti-1);
          root->right= _buildTree(preorder,inorder,prvei,rooti+1,end);
          return root;
       }

};