用二叉链表表示树，结点的值为结点的序号，创建n个结点的完全二叉树，输出前、中、后三种遍历。

以下是用C++代码实现：

#include <iostream>
using namespace std;

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

void createBinaryTree(TreeNode* &root, int num, int n) {
    if (num <= n) {
        root = new TreeNode(num);
        createBinaryTree(root->left, num * 2, n);
        createBinaryTree(root->right, num * 2 + 1, n);
    }
}

void preOrder(TreeNode* root) {
    if (root != nullptr) {
        cout << root->val << " ";
        preOrder(root->left);
        preOrder(root->right);
    }
}

void inOrder(TreeNode* root) {
    if (root != nullptr) {
        inOrder(root->left);
        cout << root->val << " ";
        inOrder(root->right);
    }
}

void postOrder(TreeNode* root) {
    if (root != nullptr) {
        postOrder(root->left);
        postOrder(root->right);
        cout << root->val << " ";
    }
}

int main() {
    int n;
    cout << "请输入结点个数n：";
    cin >> n;

    TreeNode* root = nullptr;
    createBinaryTree(root, 1, n);

    cout << "前序遍历结果：";
    preOrder(root);
    cout << endl;

    cout << "中序遍历结果：";
    inOrder(root);
    cout << endl;

    cout << "后序遍历结果：";
    postOrder(root);
    cout << endl;

    return 0;
}

其中，`createBinaryTree`函数用于创建完全二叉树，`preOrder`、`inOrder`、`postOrder`函数分别用于前序、中序、后序遍历。