POJ2253 Frogger

解题思路：floyed模板题（稍微变换一点），不解释，上代码：

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>
using namespace std;
#define inf 0x3f3f3f3f
const int maxn = 205;
double w[maxn][maxn];

struct node{
    double x, y;
}p[maxn];

int main()
{
    int n, kase = 1;
    while(~scanf("%d", &n) && n)
    {
        for(int i = 1; i <= n; i++)
        for(int j = i; j <= n; j++)
        {
            if(i == j) w[i][j] = 0;
            else w[i][j] = w[j][i] = inf;
        }

        for(int i = 1; i <= n; i++)
        scanf("%lf %lf", &p[i].x, &p[i].y);

        for(int i = 1; i <= n; i++)
        {
            for(int j = i; j <= n; j++)
            {
                double x2 = p[j].x - p[i].x;
                double y2 = p[j].y - p[i].y;

                w[i][j] = w[j][i] = sqrt(x2*x2 + y2*y2);
            }
        }

        for(int i = 1; i <= n; i++)
        {
            for(int j = 1; j <= n; j++)
            {
                for(int k = j; k <= n; k++)
                {
                    if(w[j][i] <= w[j][k] && w[i][k] <= w[j][k])
                    {
                        w[j][k] = w[k][j] = max(w[j][i], w[i][k]);
                    }
                }
            }
        }

        printf("Scenario #%d
Frog Distance = %.3lf

", kase++, w[1][2]);
    }
    return 0;
}