【POJ 2253】Frogger

【POJ 2253】Frogger

求起点到终点的通路中每天路的最大权中的最小值

最短路保证最大权联通求最小值(最短)

Floyd 524K 79MS 1170B

#include

using namespace std;

typedef struct Point
{
    int x,y;
}Point;

Point p[233];
double dis[233][233];
int n;

int dcmp(double x)
{
    return x < -esp? -1: x > esp;
}

double Dis(int a,int b)
{
    return sqrt((p[a].x-p[b].x)*(p[a].x-p[b].x)*1.0+(p[a].y-p[b].y)*(p[a].y-p[b].y)*1.0);
}

void Floyd()
{
    int i,j,k;
    for(k = 0; k < n; ++k)
    {
        for(i = 0; i < n; ++i)
        {
            for(j = 0; j < i; ++j)
            {
                if(dcmp(dis[i][j] - dis[i][k]) > 0 && dcmp(dis[i][j] - dis[k][j]) > 0)
                {
                    dis[i][j] = dis[j][i] = max(dis[i][k],dis[k][j]);
                }
            }
        }
    }
}

int main()
{
    int i,j,z = 0;
    while(~scanf("%d",&n) && n)
    {
        for(i = 0; i < n; ++i)
        {
            scanf("%d %d",&p[i].x,&p[i].y);
            for(j = 0; j <= i; ++j)
            {
                dis[j][i] = dis[i][j] = Dis(j,i);
            }
        }
        Floyd();
        printf("Scenario #%d\nFrog Distance = %.3lf\n\n",++z,dis[0][1]);
    }
    return 0;
}

Dijkstra 532K 0MS 1448B

#include

using namespace std;

typedef struct Point
{
    int x,y;
}Point;

Point p[233];
double dis[233][233];
double ds[233];
bool vis[233];
int n;

int dcmp(double x)
{
    return x < -esp? -1: x > esp;
}

double Dis(int a,int b)
{
    return sqrt((p[a].x-p[b].x)*(p[a].x-p[b].x)*1.0+(p[a].y-p[b].y)*(p[a].y-p[b].y)*1.0);
}

double Dijkstra()
{
    memset(vis,0,sizeof(vis));
    int i,p,j;
    for(i = 1; i < n; ++i) ds[i] = 111111;
    ds[0] = 0;
    double m;
    for(i = 0; i < n; ++i)
    {
        m = 111111;
        p = -1;
        for(j = 0; j < n; ++j)
        {
            if(!vis[j] && m > ds[j])
            {
                p = j;
                m = ds[j];
            }
        }
        if(p == 1) return ds[1];
        vis[p] = 1;
        for(j = 0; j < n; ++j)
        {
            if(!vis[j] && dcmp(ds[j] - ds[p]) > 0 && dcmp(ds[j] - dis[p][j]) > 0)
            {
                ds[j] = max(ds[p],dis[p][j]);
            }
        }
    }
}

int main()
{
    int i,j,z = 0;
    while(~scanf("%d",&n) && n)
    {
        for(i = 0; i < n; ++i)
        {
            scanf("%d %d",&p[i].x,&p[i].y);
            for(j = 0; j <= i; ++j)
            {
                dis[j][i] = dis[i][j] = Dis(j,i);
            }
        }
        printf("Scenario #%d\nFrog Distance = %.3lf\n\n",++z,Dijkstra());
    }
    return 0;
}

SPFA 536K 16MS 1409B

#include

using namespace std;

typedef struct Point
{
    int x,y;
}Point;

Point p[233];
double dis[233][233];
double ds[233];
bool vis[233];
int n;

int dcmp(double x)
{
    return x < -esp? -1: x > esp;
}

double Dis(int a,int b)
{
    return sqrt((p[a].x-p[b].x)*(p[a].x-p[b].x)*1.0+(p[a].y-p[b].y)*(p[a].y-p[b].y)*1.0);
}

double SPFA()
{
    memset(vis,0,sizeof(vis));
    int u,i;
    for(i = 1; i < n; ++i) ds[i] = 111111;
    ds[0] = 0;
    queue <int> q;
    q.push(0);
    while(!q.empty())
    {
        u = q.front();
        q.pop();
        vis[u] = 0;
        for(i = 0; i < n; ++i)
        {
            if(dcmp(ds[i] - dis[u][i]) > 0 && dcmp(ds[i] - ds[u]) > 0)
            {
                ds[i] = max(dis[u][i],ds[u]);
                if(!vis[i])
                {
                    vis[i] = 1;
                    q.push(i);
                }
            }
        }
    }
    return ds[1];
}

int main()
{
    int i,j,z = 0;
    while(~scanf("%d",&n) && n)
    {
        for(i = 0; i < n; ++i)
        {
            scanf("%d %d",&p[i].x,&p[i].y);
            for(j = 0; j <= i; ++j)
            {
                dis[j][i] = dis[i][j] = Dis(j,i);
            }
        }
        printf("Scenario #%d\nFrog Distance = %.3lf\n\n",++z,SPFA());
    }
    return 0;
}

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