LeetCode之Construct Binary Tree from Preorder and Inorder Traversal

 /*根据二叉树先序遍历和中序遍历的性质，递归的重建二叉树。*/
class Solution {
public:
    TreeNode* buildTree(vector<int>& preorder, vector<int>& inorder) {
        if(preorder.size() != inorder.size() || preorder.empty()) return nullptr;
        return buildTree(preorder, 0, preorder.size()-1, inorder, 0, inorder.size()-1);
    }
    
    TreeNode* buildTree(const vector<int> &preorder, int pre_left, int pre_right,
    const vector<int> &inorder, int in_left, int in_right){
        if(pre_left > pre_right) return nullptr;
        TreeNode *root = new TreeNode(preorder[pre_left]);
        int mid(in_left);
        while(mid <= in_right && inorder[mid] != preorder[pre_left]) ++mid;
        int left_length = mid - in_left;
        root->left = buildTree(preorder, pre_left+1, pre_left+left_length,
        inorder, in_left, mid-1);
        root->right = buildTree(preorder, pre_left+left_length+1, pre_right,
        inorder, mid+1, in_right);
        return root;
    }
};