把一个有序整数数组放到二叉树中

This is the first question I’m given in a google interview.

Node * array2Tree(int[] array) {
  return helper(array, 0, n-1);
}

Node * helper(int[] array, int start, int end) {
  if (start > end) return NULL;
  int m = start + (end-start)/2;
  Node * root = new Node(array[m]);
  root->left = helper(array, start, m-1);
  root->right = helper(array, m+1, end);
  return root;
}