hdu 1224 Free DIY Tour （DAG 最长路）

Problem - 1224

　　水题一枚。

　　题目的意思是给出一个DAG，找出一条回路，路径的权值的和最大，输出最大值以及其路径。

　　构出DAG以后，spfa求最长路。

代目如下：

#include <cstdio>
#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>

using namespace std;

typedef vector<int> VI;
const int N = 111;
VI rel[N];
int dis[N], pre[N], inter[N];
queue<int> Q;

void printPath(int id, int n) {
    if (pre[id] == id) return ;
    printPath(pre[id], n);
    cout << "->" << (id % n + 1);
}

int main() {
//    freopen("in", "r", stdin);
    int T, n, m;
    cin >> T;
    for (int cas = 1; cas <= T; cas++) {
        cin >> n;
        for (int i = 0; i < n; i++) {
            cin >> inter[i];
            rel[i].clear();
            pre[i] = dis[i] = 0;
        }
        inter[n] = dis[n] = pre[n] = 0;
        rel[n].clear();
        cin >> m;
        int u, v;
        for (int i = 0; i < m; i++) {
            cin >> u >> v;
            u--, v--;
            if (u > v) swap(u, v);
            rel[u].push_back(v);
//            cout << u << ' ' << v << endl;
        }
        while (!Q.empty()) Q.pop();
        Q.push(0);
        while (!Q.empty()) {
            int cur = Q.front();
//            cout << cur << endl;
            Q.pop();
            for (int i = 0, endi = rel[cur].size(); i < endi; i++) {
                int t = rel[cur][i];
//                cout << "t " << t << endl;
                if (dis[t] < dis[cur] + inter[t]) {
                    dis[t] = dis[cur] + inter[t];
                    pre[t] = cur;
                    Q.push(t);
                }
            }
        }
        printf("CASE %d#\n", cas);
        cout << "points : " << dis[n] << endl;
        cout << "circuit : 1";
        printPath(n, n);
        cout << endl;
        if (cas < T) cout << endl;
    }
    return 0;
}

——written by Lyon