DAG图拓扑 + dp

#include<cstdio>
#include<iostream>
#include<cstring>
#include<algorithm>
#include<vector>
#include<queue>
#include<stack>
using namespace std;
int n, m, T;
struct Node
{
    int to;
    int dis;
    Node(){}
    Node(int x, int y)
    {
        to = x;
        dis = y;
    }
};
const int maxn = 5050;
const int INF = 0x3f3f3f3f;
int indeg[maxn];
queue<int> q;
vector<Node> g[maxn];
int dp[maxn][maxn];
int pre[maxn][maxn];


void topsort()
{
    /*
    for(int i = 1; i <= n; i++)
        if(!indeg[i])
            cout << i << "  ";
    cout << endl;
    */

    queue<int> tmp;
    for(int i = 1; i <= n; i++)
    {
        if(indeg[i] == 0)
        {
            cout << "insert into tmp: " << i << endl;
            tmp.push(i);
        }
    }
    cout << "tmp seq is: " << endl;

    while(!tmp.empty())
    {
        int u = tmp.front();
        q.push(u);
        tmp.pop();
        cout << u << " " ;
        cout << g[u].size() << " ";

        for(int i = 0; i < (int)g[u].size(); i++)
        {
            int t = g[u][i].to;
            indeg[t]--;
            if(!indeg[t])
                tmp.push(t);
        }
    }
    cout << endl;
}


int main()
{
    int n;
    cin >> n >> m >> T;
    int a, b, c;
    for(int i = 0; i < m; i++)
    {
        cin >> a >> b >> c;
        g[a].push_back(Node(b, c));     //correct
        indeg[b]++;
    }

    //topsort();                  //wrong
    queue<int> tmp;
    for(int i = 1; i <= n; i++)
    {
        if(indeg[i] == 0)
        {
            tmp.push(i);
        }
    }
    //cout << "tmp seq is: " << endl;

    while(!tmp.empty())
    {
        int u = tmp.front();
        q.push(u);
        tmp.pop();
        //cout << u << " " ;

        for(int i = 0; i < (int)g[u].size(); i++)
        {
            int t = g[u][i].to;
            indeg[t]--;
            if(!indeg[t])
                tmp.push(t);
        }
    }

    for(int i = 1; i <= n; i++)
        for(int j = 0; j < n; j++)
            dp[i][j] = INF;　　　　　　//dp[i][j]表示走到点i经过j个点（不包括终点i)的时间
    dp[1][0] = 0;

    while(!q.empty())
    {
        int now = q.front();
        q.pop();

        for(int i = 0; i < (int)g[now].size(); i++)
        {
            int to = g[now][i].to;
            int dis = g[now][i].dis;
            for(int j = 1; j < n; j++)  //
            {
                if(dp[now][j - 1] + dis < dp[to][j])
                {
                    dp[to][j] = dp[now][j - 1] + dis;
                    pre[to][j] = now;
                }
            }
        }
    }
 
    int max_num = 0;

    for(int i = 0; i < n; i++)
    {
        if(dp[n][i] <= T)
        {
            max_num = i;
        }
    }
    cout << max_num + 1<< endl;    //因为dp表示的是经过的点，所以终点需+1
    int num = max_num;
    int cur = n;
    stack<int> st;
    while(cur != 1)　　　　//存路径
    {        
        st.push(cur);
        cur = pre[cur][num];
        num = num - 1;
    }
    cout << "1" << " ";　　
    while(!st.empty())
    {
        cout << st.top() << " ";
        st.pop();
    }
    return 0;
}