Palindrome Construct Binary Tree from Preorder and Inorder Traversal

// 156ms 过大的
 1 /**
 * Definition for binary tree
 * 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,int pb,int pe, vector<int> &inorder,int ib,int ie)
    {
        TreeNode *root=new TreeNode(0);
        root->val=preorder[pb];
        
        vector<int>::iterator proot=find(inorder.begin(),inorder.end(),root->val);
        int pos=proot-inorder.begin();
        
        int leftLen=pos-ib;
        int rightLen=ie-pos;
        
        if(leftLen>0)
            root->left=buildTree(preorder,pb+1,pb+leftLen,inorder,ib,pos-1);
        if(rightLen>0)
            root->right=buildTree(preorder,pb+leftLen+1,pe,inorder,pos+1,ie);
        return root;
    }
    
    TreeNode *buildTree(vector<int> &preorder, vector<int> &inorder) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        if(preorder.size()==0)
            return NULL;
        return buildTree(preorder,0,preorder.size()-1,inorder,0,preorder.size()-1);
    }
};