重建二叉树

struct BTNode {
int val;
BTNode *lchild;
BTNode *rchild;
BTNode(int x): val(x), lchild(NULL), rchild(NULL){}
};

BTNode* rebuildBinTree(int a[], int b[], int n)
{
if (n <= 0)
return NULL;
BTNode *root = new BTNode(a[0]);
int i;
for (i = 0; i < n; ++i)
{
if (b[i] == a[0])
break;
}
root->lchild = rebuildBinTree(a+1, b, i);
root->rchild = rebuildBinTree(a+i+1, b+i+1,n-i-1);
return root;
}