二叉树的先序后续中序代码完整代码

以下是二叉树的先序、中序、后序遍历的完整代码实现（C++语言）：

#include <iostream>
using namespace std;

struct TreeNode {
    int val;
    TreeNode* left;
    TreeNode* right;
    TreeNode(int x) : val(x), left(NULL), right(NULL) {}
};

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

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

    vector<int> preorderTraversal(TreeNode* root) {
        vector<int> res;
        preorder(root, res);
        return res;
    }

    void preorder(TreeNode* root, vector<int>& res) {
        if (root == NULL) {
            return;
        }
        res.push_back(root->val);
        preorder(root->left, res);
        preorder(root->right, res);
    }

    vector<int> inorderTraversal(TreeNode* root) {
        vector<int> res;
        inorder(root, res);
        return res;
    }

    void inorder(TreeNode* root, vector<int>& res) {
        if (root == NULL) {
            return;
        }
        inorder(root->left, res);
        res.push_back(root->val);
        inorder(root->right, res);
    }

    vector<int> postorderTraversal(TreeNode* root) {
        vector<int> res;
        postorder(root, res);
        return res;
    }

    void postorder(TreeNode* root, vector<int>& res) {
        if (root == NULL) {
            return;
        }
        postorder(root->left, res);
        postorder(root->right, res);
        res.push_back(root->val);
    }
};

其中，`buildTree` 函数用来构建二叉树，`preorderTraversal` 函数用来进行先序遍历，`inorderTraversal` 函数用来进行中序遍历，`postorderTraversal` 函数用来进行后序遍历。