Leetcode 之Construct Binary Tree（52）

//中序和后序
TreeNode *buildTree1(vector<int>& inorder, vector<int>& postorder)
{
return buildTree1(begin(inorder), end(inorder), begin(postorder), begin(postorder));
}
template<typename InputIterator>
TreeNode *buildTree1(InputIterator in_first, InputIterator in_last,
InputIterator post_first, InputIterator post_last)
{
if (in_first == in_last)return nullptr;
if (post_first == post_last)return nullptr;
//后序最后一个为根结点
const auto val = *prev(post_last)
auto root = new TreeNode(val);
//查找根结点在中序的位置，返回的是迭代器
auto intRootPos = find(in_first, in_last, val);
//得到根结点的左半部分
auto leftSize = distance(in_first, intRootPos);
//递归构造，注意去掉根结点
root->left = buildTree(in_first, intRootPos,
post_first, next(post_first, leftSize));
root->right = buildTree(next(intRootPos), in_last,
next(post_first,leftSize), prev(post_last));

return root;
}