Codeforces Round #374 (Div. 2) C. Journey DP

C. Journey

题目连接：

http://codeforces.com/contest/721/problem/C

Description

Recently Irina arrived to one of the most famous cities of Berland — the Berlatov city. There are n showplaces in the city, numbered from 1 to n, and some of them are connected by one-directional roads. The roads in Berlatov are designed in a way such that there are no cyclic routes between showplaces.

Initially Irina stands at the showplace 1, and the endpoint of her journey is the showplace n. Naturally, Irina wants to visit as much showplaces as she can during her journey. However, Irina's stay in Berlatov is limited and she can't be there for more than T time units.

Help Irina determine how many showplaces she may visit during her journey from showplace 1 to showplace n within a time not exceeding T. It is guaranteed that there is at least one route from showplace 1 to showplace n such that Irina will spend no more than T time units passing it.

Input

The first line of the input contains three integers n, m and T (2 ≤ n ≤ 5000,  1 ≤ m ≤ 5000,  1 ≤ T ≤ 109) — the number of showplaces, the number of roads between them and the time of Irina's stay in Berlatov respectively.

The next m lines describes roads in Berlatov. i-th of them contains 3 integers ui, vi, ti (1 ≤ ui, vi ≤ n, ui ≠ vi, 1 ≤ ti ≤ 109), meaning that there is a road starting from showplace ui and leading to showplace vi, and Irina spends ti time units to pass it. It is guaranteed that the roads do not form cyclic routes.

It is guaranteed, that there is at most one road between each pair of showplaces.

Output

Print the single integer k (2 ≤ k ≤ n) — the maximum number of showplaces that Irina can visit during her journey from showplace 1 to showplace n within time not exceeding T, in the first line.

Print k distinct integers in the second line — indices of showplaces that Irina will visit on her route, in the order of encountering them.

If there are multiple answers, print any of them

Sample Input

4 3 13
1 2 5
2 3 7
2 4 8

Sample Output

3
1 2 4

Hint

题意

给你一个n点m边的图，让你从1走到n，找到一条经过尽量多点的路径，且路径边权和小于等于T

然后输出路径。

题解：

直接DP，DP[i][j]表示在i点，当前经过了j个点的最小代价是多少

然后暴力转移就好了。

代码

#include<bits/stdc++.h>
using namespace std;
const int maxn = 5005;
int dp[maxn][maxn],pre[maxn][maxn],n,m;
int k;
vector<int>E[maxn];
vector<int>val[maxn];
void dfs(int x,int num,int sp,int fa)
{
    if(dp[x][num]<=sp)return;
    dp[x][num]=sp;pre[x][num]=fa;
    for(int i=0;i<E[x].size();i++)
        if(sp+val[x][i]<=k)
            dfs(E[x][i],num+1,sp+val[x][i],x);
}
vector<int> ppp;
void dfs2(int x,int y)
{
    ppp.push_back(x);
    if(pre[x][y]==-1)
    {
        cout<<ppp.size()<<endl;
        for(int i=ppp.size()-1;i>=0;i--)
            cout<<ppp[i]<<" ";
        cout<<endl;
        return;
    }
    else
        dfs2(pre[x][y],y-1);
}
int main()
{
    memset(pre,-1,sizeof(pre));
    for(int i=0;i<maxn;i++)
        for(int j=0;j<maxn;j++)
            dp[i][j]=1e9+7;
    scanf("%d%d%d",&n,&m,&k);
    for(int i=1;i<=m;i++)
    {
        int a,b,c;
        scanf("%d%d%d",&a,&b,&c);
        E[a].push_back(b);
        val[a].push_back(c);
    }
    dfs(1,1,0,-1);
    for(int i=n;i>=2;i--)
    {
        if(dp[n][i]<=k)
        {
            dfs2(n,i);
            break;
        }
    }
}

转载于:https://www.cnblogs.com/qscqesze/p/5925887.html