zoukankan      html  css  js  c++  java
  • UVA 10816 Travel in Desert 最短路+二分

    --------------------

    Description

    There is a group of adventurers who like to travel in the desert. Everyone knows travelling in desert can be very dangerous. That's why they plan their trip carefully every time. There are a lot of factors to consider before they make their final decision.

    One of the most important factors is the weather. It is undesirable to travel under extremely high temperature. They always try to avoid going to the hottest place. However, it is unavoidable sometimes as it might be on the only way to the destination. To decide where to go, they will pick a route that the highest temperature is minimized. If more than one route satisfy this criterion, they will choose the shortest one.

    There are several oases in the desert where they can take a rest. That means they are travelling from oasis to oasis before reaching the destination. They know the lengths and the temperatures of the paths between oases. You are to write a program and plan the route for them.

    Input

    Input consists of several test cases. Your program must process all of them.

    The first line contains two integers N and E (1 ≤ N ≤ 100; 1 ≤ E ≤ 10000) where N represents the number of oasis and E represents the number of paths between them. Next line contains two distinct integers S and T (1 ≤ ST ≤ N) representing the starting point and the destination respectively. The following E lines are the information the group gathered. Each line contains 2 integers X, Y and 2 real numbers R and D (1 ≤ XY ≤ N; 20 ≤ R ≤ 50; 0 < D ≤ 40). It means there is a path between X and Y, with length D km and highest temperature oC. Each real number has exactly one digit after the decimal point. There might be more than one path between a pair of oases.

    Output

    Print two lines for each test case. The first line should give the route you find, and the second should contain its length and maximum temperature.

    Sample Input

    6 9
    1 6
    1 2 37.1 10.2
    2 3 40.5 20.7
    3 4 42.8 19.0
    3 1 38.3 15.8
    4 5 39.7 11.1
    6 3 36.0 22.5
    5 6 43.9 10.2
    2 6 44.2 15.2
    4 6 34.2 17.4

    Sample Output

    1 3 6
    38.3 38.3


    --------------------

    选一条温度最低且长度最短的路线。

    二分温度,跑最短路即可。

    --------------------

    #include <iostream>
    #include <cstdio>
    #include <cstring>
    #include <algorithm>
    #include <queue>
    using namespace std;
    const int maxn=211;
    const int maxm=21111;
    const int INF=0x3f3f3f3f;
    const double OO=1e100;
    const double eps=1e-6;
    struct EdgeNode{
        int to;
        double w;
        double T;
        int next;
    };
    
    struct HeapNode{
        int d,u;
        bool operator<(const HeapNode& rhs) const{
            return d>rhs.d;
        }
    };
    
    struct Dijkstra{
        EdgeNode edges[maxm];
        int head[maxn];
        int edge,n;
        void init(int n){
            this->n=n;
            memset(head,-1,sizeof(head));
            edge=0;
        }
        void addedges(int u,int v,double w,double t){
            edges[edge].w=w,edges[edge].T=t,edges[edge].to=v,edges[edge].next=head[u],head[u]=edge++;
        }
        bool done[maxn];
        double dis[maxn];
        int pre[maxn];
        bool dijkstra(int s,int t,double c){
            priority_queue<HeapNode>que;
            for (int i=0;i<=n;i++) dis[i]=OO;
            dis[s]=0;
            memset(done,0,sizeof(done));
            que.push((HeapNode){0,s});
            while (!que.empty()){
                HeapNode x=que.top();
                que.pop();
                int u=x.u;
                if (done[u]) continue;
                done[u]=true;
                for (int i=head[u];i!=-1;i=edges[i].next){
                    int v=edges[i].to;
                    double w=edges[i].w;
                    double tm=edges[i].T;
                    if (tm<=c&&dis[v]>dis[u]+w){
                        dis[v]=dis[u]+w;
                        pre[v]=u;
                        que.push((HeapNode){dis[v],v});
                    }
                }
            }
            if (dis[t]<OO) return true;
            return false;
        }
        void output(int s,int t){
            if (s!=t) output(s,pre[t]);
            else{
                printf("%d",s);
                return;
            }
            printf(" %d",t);
        }
    }solver;
    int n,m;
    int s,t;
    int main()
    {
        while (~scanf("%d%d",&n,&m)){
            double l=OO;
            double r=0;
            scanf("%d%d",&s,&t);
            solver.init(n);
            for (int i=0;i<m;i++){
                int x,y;
                double w,tm;
                scanf("%d%d%lf%lf",&x,&y,&tm,&w);
                solver.addedges(x,y,w,tm);
                solver.addedges(y,x,w,tm);
                l=min(l,tm);
                r=max(r,tm);
            }
            while (r-l>eps){
                double mid=(l+r)/2;
                if (solver.dijkstra(s,t,mid)){
                    r=mid;
                }
                else{
                    l=mid;
                }
            }
            solver.dijkstra(s,t,r);
            solver.output(s,t);
            printf("
    ");
            printf("%0.1f %0.1f
    ",solver.dis[t],r);
        }
        return 0;
    }
    


    --------------------

    --------------------

    --------------------

  • 相关阅读:
    数据库操作,内外联查询,分组查询,嵌套查询,交叉查询,多表查询,语句小结
    重复控件Repeater和数据列表控件DataList
    网格视图控件GridView (2)
    用好VS2005之扩展membership服务(1)
    5.4 网格视图控件GridView (1)
    数据源控件
    ASP.NET程序中常用的三十三种代码
    在DataSet和DataReader之间选择
    自定义ASP.net 2.0 Membership的步骤,和entry 'AspNetSqlMembershipProvider' has already been added错误的解决
    INNER JOIN
  • 原文地址:https://www.cnblogs.com/cyendra/p/3681568.html
Copyright © 2011-2022 走看看