/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     struct TreeNode *left;
 *     struct TreeNode *right;
 * };
 */
struct TreeNode* help(int* pre,int* in,int n)
{
    if(pre==NULL||in==NULL||n==0)
    return NULL;
    else
    {
       struct TreeNode* s=(struct TreeNode*)malloc(sizeof(struct TreeNode));
       s->val=*pre;
       int i;
       int* p;
       for(p=in;p<in+n;++p)
       {
           if(*p==*pre)
           break;
       }
       i=p-in;
       s->left=help(pre+1,in,i);
       s->right=help(pre+i+1,p+1,n-i-1);
       return s;
    }
}
struct TreeNode* buildTree(int* preorder, int preorderSize, int* inorder, int inorderSize){
    int n=preorderSize;
    struct TreeNode*root=help(preorder,inorder,n);
    return root;
}