hdu 4571 Travel in time

本文介绍了一种旅行规划算法,旨在帮助用户在有限的时间内选择最佳景点访问顺序以最大化满意度。通过考虑时间成本、满意度价值及特定需求,算法使用图论与动态规划解决复杂路径规划问题。

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Problem Description
  Bob gets tired of playing games, leaves Alice, and travels to Changsha alone. Yuelu Mountain, Orange Island, Window of the World, the Provincial Museum etc...are scenic spots Bob wants to visit. However, his time is very limited, he can’t visit them all. 
  Assuming that there are N scenic spots in Changsha, Bob defines a satisfaction value Si to each spot. If he visits this spot, his total satisfaction value will plus Si. Bob hopes that within the limited time T, he can start at spot S, visit some spots selectively, and finally stop at spot E, so that the total satisfaction value can be as large as possible. It's obvious that visiting the spot will also cost some time, suppose that it takes Ci units of time to visit spot i ( 0 <= i < N ).
  Always remember, Bob can choose to pass by a spot without visiting it (including S and E), maybe he just want to walk shorter distance for saving time. 
  Bob also has a special need which is that he will only visit the spot whose satisfaction value is strictly larger than that of which he visited last time. For example, if he has visited a spot whose satisfaction value is 50, he would only visit spot whose satisfaction value is 51 or more then. The paths between the spots are bi-directional, of course.
 

Input
  The first line is an integer W, which is the number of testing cases, and the W sets of data are following.
  The first line of each test data contains five integers: N M T S E. N represents the number of spots, 1 < N < 100; M represents the number of paths, 0 < M < 1000; T represents the time limitation, 0 < T <= 300; S means the spot Bob starts from. E indicates the end spot. (0 <= S, E < N)
  The second line of the test data contains N integers Ci ( 0 <= Ci <= T ), which means the cost of time if Bob visits the spot i.
  The third line also has N integers, which means the satisfaction value Si that can be obtained by visiting the spot i ( 0 <= Si < 100 ).
  The next M lines, each line contains three integers u v L, means there is a bi-directional path between spot u and v and it takes L units of time to walk from u to v or from v to u. (0 <= u, v < N, 0 <= L <= T)
 

Output
  Output case number in the first line (formatted as the sample output).
  The second line contains an integer, which is the greatest satisfaction value.
If Bob can’t reach spot E in T units of time, you should output just a “0” (without quotation marks).
 

Sample Input
1 4 4 22 0 3 1 1 1 1 5 7 9 12 0 1 10 1 3 10 0 2 10 2 3 10
 

Sample Output
Case #1: 21
 

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>
using namespace std;
const int inf=1<<29;
const int maxn=102;///城市数量
const int maxm=505;///时间花费
int T,n,m,t,s,e,cas=1;
int map[maxm][maxn];
int dp[maxm][maxm],pos[maxn];
struct node
{
    int val,cos,id;
    friend bool operator<(node x,node y)
    {
        return x.val<y.val;
    }
} p[maxn];
void read()
{
    int i,j,u,v,c;
    cin>>n>>m>>t>>s>>e;
    memset(pos,0,sizeof(pos));
    for(i=0; i<n; i++)cin>>p[i].cos;
    for(i=0; i<n; i++)cin>>p[i].val,p[i].id=i;
    sort(p,p+n);
    for(i=0; i<n; i++)pos[p[i].id]=i;
    s=pos[s],e=pos[e];
    for(i=0; i<n; i++)
    {
        for(j=0; j<n; j++)map[i][j]=inf;
        map[i][i]=0;
    }
     for(i=0; i<n; i++)
    {
        for(j=0; j<=t; j++)dp[i][j]=0;
    }
    while(m--)
    {
        cin>>u>>v>>c;
        u=pos[u],v=pos[v];
        map[u][v]=map[v][u]=min(c,map[u][v]);
    }
}
void floyd()
{
    int i,j,k;
    for(k=0; k<n; k++)
        for(i=0; i<n; i++)
            for(j=0; j<n; j++)
                map[i][j]=min(map[i][j],map[i][k]+map[k][j]);
}
int solve()
{
    int i,j,k,tmp,ans=0;
    if(map[s][e]>t)return 0;
    for(i=0; i<n; i++)///到第i个点,最少时间花费下的满意值
    {
        for(j=map[s][i]+p[i].cos; j<=t; j++)
            dp[i][j]=p[i].val;
    }
    for(i=0; i<n; i++)///e在游览路径中
    {
        for(j=0; j<i; j++)
        {
            if(p[i].val>p[j].val)
            {
                int key=map[j][i]+p[i].cos+map[s][j];
                for(k=t-key;k>=0; k--)
                {
                    tmp=k+map[s][j];
                    dp[i][key+k]=max(dp[j][tmp]+p[i].val,dp[i][key+k]);
                }
            }
        }
    }
    ans=dp[e][t];///e在游览路径中的最大值
    for(i=0; i<n; i++)///e不在游览路径中的最大值
    {
        if(i!=e)
        {
            if(t-map[i][e]>=map[s][i])
            {
                ans=max(ans,dp[i][t-map[i][e]]);
            }
        }
    }
    return ans;
}
int main()
{
    cin>>T;
    while(T--)
    {
        read();
        floyd();
        printf("Case #%d:\n%d\n",cas++,solve());
    }
    return 0;
}


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