骑马修栅栏(Riding the Fences) 题解

思路分析

按题目要求使用对应数据结构与算法模拟/递推求解，注意数据范围边界与时间复杂度。

参考代码

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

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int m;
    if (!(cin >> m)) return 0;
    const int MAXV = 500;
    vector<vector<int>> cnt(MAXV + 1, vector<int>(MAXV + 1, 0));
    vector<int> deg(MAXV + 1, 0);
    for (int i = 0; i < m; ++i) {
        int u, v;
        cin >> u >> v;
        cnt[u][v]++;
        cnt[v][u]++;
        deg[u]++;
        deg[v]++;
    }
    int start = 1;
    for (int i = 1; i <= MAXV; ++i) {
        if (deg[i] > 0) {
            start = i;
            break;
        }
    }
    for (int i = 1; i <= MAXV; ++i) {
        if (deg[i] % 2 == 1) {
            start = i;
            break;
        }
    }
    vector<int> stk, ans;
    vector<int> cur_v(MAXV + 1, 1);
    stk.push_back(start);
    while (!stk.empty()) {
        int u = stk.back();
        while (cur_v[u] <= MAXV && cnt[u][cur_v[u]] == 0) {
            cur_v[u]++;
        }
        if (cur_v[u] <= MAXV) {
            int v = cur_v[u];
            cnt[u][v]--;
            cnt[v][u]--;
            stk.push_back(v);
        } else {
            ans.push_back(u);
            stk.pop_back();
        }
    }
    reverse(ans.begin(), ans.end());
    for (int x : ans) {
        cout << x << "\n";
    }
    return 0;
}