解法一：排序

先要按照输入数据构建链表，因为可能会有无效结点。

#include <bits/stdc++.h>
using namespace std;
class Node {
public:
    string address;
    int key;
    string next;
};
bool cmp(Node &o1, Node &o2) {
    return o1.key < o2.key;
}
int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int N;
    string head;
    cin >> N >> head;
    vector<Node> list;
    map<string, Node> nodeMap;
    for (int i = 0; i < N; ++i) {
        Node node;
        cin >> node.address >> node.key >> node.next;
        nodeMap.emplace(node.address, node);
    }
    while (head != "-1") {
        auto res = nodeMap.find(head);
        list.emplace_back(res->second);
        head = res->second.next;
    }
    if (list.empty()) {
        cout << "0 -1\n";
        return 0;
    }
    sort(list.begin(), list.end(), cmp);
    for (int i = 0; i < list.size() - 1; ++i) {
        list[i].next = list[i + 1].address;
    }
    list[list.size() - 1].next = "-1";
    cout << list.size() << " " << list[0].address << "\n";
    for (auto &it:list) {
        cout << it.address << " " << it.key << " " << it.next << "\n";
    }
}