力扣106. 从中序与后序遍历序列构造二叉树

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    TreeNode* buildTree(vector<int>& inorder, vector<int>& postorder) {
        if(postorder.size() == 0) return nullptr;
        int rootvalue = postorder[postorder.size() - 1];
        TreeNode* root = new TreeNode(rootvalue);
        if(postorder.size() == 0) return root;
        int index;
        for(index = 0; index < inorder.size(); index++) {
            if(inorder[index] == rootvalue) break;
        }
        vector<int> inorder_left(inorder.begin(), inorder.begin() + index);
        vector<int> inorder_right(inorder.begin() + index + 1, inorder.end());
        vector<int> postorder_left(postorder.begin(), postorder.begin() + index);
        vector<int> postorder_right(postorder.begin() + index, postorder.end() - 1);
        root->left = buildTree(inorder_left, postorder_left);
        root->right = buildTree(inorder_right, postorder_right);
        return root;
    }
};