POJ2253 Frogger

题意：

在第一块石头到到第二块石头的通路中，每一条通路的元素都是这条通路中前后两个点的距离，这些距离中有一个最大距离，如果有多条通路，则求出所有通路的最大距离，并把这些最大距离作比较，把最小的一个最大距离输出。    

dijkstra和spfa 写的  总感觉还是dijkstra比较好理解  。。。。。。  做了poj1797后 才发现 果然还是spfa最好用

spfa：

#include <iostream>
#include <cstdio>
#include <cstring>
#include <queue>
#include <cmath>
#define mem(a,b) memset(a,b,sizeof(a))
using namespace std;
const int maxn = 101000, INF = 0xfffffff;
int head[maxn],vis[maxn];
double d[maxn];
int n;
struct tmp{
    double x,y;
}Tmp[maxn];

struct node{
    int u,v,next;
    double d;
}Node[maxn];

void add(int u,int v,double d,int i)
{
    Node[i].u = u;
    Node[i].v = v;
    Node[i].d = d;
    Node[i].next = head[u];
    head[u] = i;
}
void spfa(int s)
{
    mem(vis,0);
    queue<int> Q;
    for(int i=0;i<=n;i++) d[i] = INF;
    d[s] = 0;
    Q.push(s);
    vis[s] = 1;
    while(!Q.empty())
    {
        int x = Q.front();Q.pop();
        vis[x] = 0;
        for(int i=head[x]; i!=-1; i=Node[i].next)
        {
            node e = Node[i];
            if(d[e.v] > max(d[x],e.d))
            {
                d[e.v] = max(d[x],e.d);
                if(!vis[e.v])
                {
                    Q.push(e.v);
                    vis[e.v] = 1;
                }
            }
        }
    }
}
int main()
{
    int ans = 0;
    while(cin>>n && n)
    {
        int cnt = 0;
        mem(head,-1);
        for(int i=1;i<=n;i++)
        {
            cin>>Tmp[i].x>>Tmp[i].y;
        }
        for(int i=1;i<=n;i++)
        {
            for(int j=i;j<=n;j++)
            {
                add(i,j,sqrt((Tmp[i].x-Tmp[j].x)*(Tmp[i].x-Tmp[j].x) + (Tmp[i].y-Tmp[j].y)*(Tmp[i].y-Tmp[j].y)),cnt++);
                add(j,i,sqrt((Tmp[i].x-Tmp[j].x)*(Tmp[i].x-Tmp[j].x) + (Tmp[i].y-Tmp[j].y)*(Tmp[i].y-Tmp[j].y)),cnt++);
            }

        }
        spfa(1);
        printf("Scenario #%d\n",++ans);
        printf("Frog Distance = %.3f\n",d[2]);
        cout<<endl;

    }




    return 0;
}

 

 

dijkstra:

#include <iostream>
#include <cstdio>
#include <cstring>
#include <vector>
#include <queue>
#include <cmath>
#define mem(a,b) memset(a,b,sizeof(a))
using namespace std;
const int maxn = 10010, INF = 0xfffffff;
int n,m;
int vis[maxn];
double d[maxn];
struct node2{
    double x,y;
}Node[maxn];


struct edge{
    int u,v;
    double d;
    edge(int u,int v,double d)
    {
        this->u = u;
        this->v = v;
        this->d = d;

    }

};
vector<edge> Edge;
vector<int> G[maxn];
struct node{
    int u;
    double d;
    node(double d,int u)
    {
        this->d = d;
        this->u = u;

    }
    bool operator < (const node& a) const {
        return d > a.d;
    }
};
void add(int u,int v,double d)
{
    Edge.push_back(edge(u,v,d));
    G[u].push_back(Edge.size()-1);
}
void dijkstra(int s)
{
    priority_queue<node> Q;
    for(int i=0;i<=n;i++) d[i] = INF;
    d[s] = 0;
    mem(vis,0);
    Q.push(node(0,s));
    while(!Q.empty())
    {
        node x = Q.top();Q.pop();
        int u = x.u;
        if(vis[u]) continue;
        vis[u] = 1;
        for(int i=0;i<G[u].size();i++)
        {
            edge e = Edge[G[u][i]];
            if(d[e.v] > max(d[u], e.d))
            {
                d[e.v] = max(d[u], e.d);
                Q.push(node(d[e.v],e.v));
            }
        }
    }
}



int main()
{
    int cnt = 0;
    while(cin>>n && n)
    {
        for(int i=0;i<=n;i++) G[i].clear();
        Edge.clear();
        for(int i=1;i<=n;i++)
        {
            cin>>Node[i].x>>Node[i].y;
        }
        for(int i=1;i<=n;i++)
            for(int j=i;j<=n;j++)
            {
                add(i,j,sqrt((Node[i].x-Node[j].x)*(Node[i].x-Node[j].x)+(Node[i].y-Node[j].y)*(Node[i].y-Node[j].y)));
                add(j,i,sqrt((Node[i].x-Node[j].x)*(Node[i].x-Node[j].x)+(Node[i].y-Node[j].y)*(Node[i].y-Node[j].y)));
            }
        dijkstra(1);
        printf("Scenario #%d\n",++cnt);
        printf("Frog Distance = %.3f\n",d[2]);
        cout<<endl;
    }
    return 0;
}

 

 

Floyd：

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#define mem(a,b) memset(a,b,sizeof(b))
using namespace std;
const int maxn = 202, INF = 2000;
struct edge{
    double x,y;
}Edge[maxn];
double d[maxn][maxn];
int main()
{
    int n,cnt = 0;
    while(cin>>n && n)
    {

        for(int i=1;i<=n;i++)
            cin>>Edge[i].x>>Edge[i].y;
        for(int i=1;i<=n;i++)
            for(int j=1;j<=n;j++)
                d[i][j] = d[j][i] = sqrt(pow(Edge[i].x-Edge[j].x,2)+pow(Edge[i].y-Edge[j].y,2));
        for(int k=1;k<=n;k++)
            for(int i=1;i<=n;i++)
                for(int j=1;j<=n;j++)
                    d[i][j] = min(d[i][j],max(d[i][k],d[k][j]));
        printf("Scenario #%d\n",++cnt);
        printf("Frog Distance = %.3f\n",d[1][2]);
        cout<<endl;
    }

    return 0;
}