lintcode- 前序遍历和中序遍历树构造二叉树-73

/**
* Definition of TreeNode:
* class TreeNode {
* public:
*     int val;
*     TreeNode *left, *right;
*     TreeNode(int val) {
*         this->val = val;
*         this->left = this->right = NULL;
*     }
* }
*/

class Solution {
public:
TreeNode *buildTree(vector<int> &pre,vector<int> &in,int ps,int pe,int is,int ie){
int record=pre[ps];
TreeNode *root= new TreeNode(record);
if(ps==pe)
return root;
int i;
for(i=is;i<=ie;++i)
if(in[i]==record)
break;
if(is<=i-1)
root->left =buildTree(pre,in,ps+1,ps+(i-is),is,i-1);
if(i+1<=ie)
root->right=buildTree(pre,in,ps+(i-is)+1,pe,i+1,ie);
return root;
}
TreeNode *buildTree(vector<int> &preorder, vector<int> &inorder) {
if(inorder.empty()&&preorder.empty())
return nullptr;

if(inorder.size()!=preorder.size())
return nullptr;
return buildTree(preorder,inorder,0,preorder.size()-1,0,inorder.size()-1);
}
};