[jobdu]二叉树的镜像

树的镜像，这里的做法就是先序遍历的反过来呗。

#include <iostream>
#include <vector>
using namespace std;

void preOrder(vector<vector<int> > &tree, vector<int> &val, vector<int> &ans, int root) {
    if (root == -1) return;
    else {
        ans.push_back(val[root]);
        preOrder(tree, val, ans, tree[root][1]);
        preOrder(tree, val, ans, tree[root][0]);
    }
}

int main() {
    int n;
    while (cin >> n)
    {
        vector<vector<int> > tree(n+1);
        vector<int> val(n+1);
        for (int i = 1; i <= n; i++) {
            int tmp;
            cin >> tmp;
            val[i] = tmp;
        }
        for (int i = 1; i <= n; i++) {
            char type;
            cin >> type;
            if (type == 'd') {
                int x, y;
                cin >> x >> y;
                tree[i].push_back(x);
                tree[i].push_back(y);
            }
            else if (type == 'l') {
                int x;
                cin >> x;
                tree[i].push_back(x);
                tree[i].push_back(-1);
            }
            else if (type == 'r') {
                int x;
                cin >> x;
                tree[i].push_back(-1);
                tree[i].push_back(x);
            }
            else if (type == 'z') {
                tree[i].push_back(-1);
                tree[i].push_back(-1);
            }
        }
        if (n == 0) {
            cout << "NULL" << endl;
            continue;
        }
        vector<int> ans;
        preOrder(tree, val, ans, 1);
        for (int i = 0; i < ans.size() - 1; i++) {
            cout << ans[i] << " ";
        }
        cout << ans[ans.size()-1] << endl;
    }
}