假设一棵二叉树的先序序列为EBADCFHGIKJ，中序序列为ABCDEFGHIJK，请画出该二叉树，并写出后序序列。数据结构代码

二叉树的节点结构体定义如下：

struct TreeNode {
    char val;
    TreeNode* left;
    TreeNode* right;
    TreeNode(char x) : val(x), left(nullptr), right(nullptr) {}
};

可以通过递归构建二叉树，具体实现如下：

class Solution {
public:
    TreeNode* buildTree(vector<char>& preorder, vector<char>& inorder) {
        return build(preorder, inorder, 0, preorder.size() - 1, 0, inorder.size() - 1);
    }

private:
    TreeNode* build(vector<char>& preorder, vector<char>& inorder, int preStart, int preEnd, int inStart, int inEnd) {
        if (preStart > preEnd || inStart > inEnd) {
            return nullptr;
        }
        char rootVal = preorder[preStart];
        int index = 0;
        for (int i = inStart; i <= inEnd; i++) {
            if (inorder[i] == rootVal) {
                index = i;
                break;
            }
        }
        int leftSize = index - inStart;
        TreeNode* root = new TreeNode(rootVal);
        root->left = build(preorder, inorder, preStart + 1, preStart + leftSize, inStart, index - 1);
        root->right = build(preorder, inorder, preStart + leftSize + 1, preEnd, index + 1, inEnd);
        return root;
    }
};

构建完成后，可以进行后序遍历，得到后序序列：

class Solution {
public:
    vector<char> postorderTraversal(TreeNode* root) {
        vector<char> result;
        postorder(root, result);
        return result;
    }

private:
    void postorder(TreeNode* root, vector<char>& result) {
        if (root == nullptr) {
            return;
        }
        postorder(root->left, result);
        postorder(root->right, result);
        result.push_back(root->val);
    }
};