Frogger

Posted 2020-10-04 小时のblog

Frogger

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 48662		Accepted: 15490

Description

Freddy Frog is sitting on a stone in the middle of a lake. Suddenly he notices Fiona Frog who is sitting on another stone. He plans to visit her, but since the water is dirty and full of tourists‘ sunscreen, he wants to avoid swimming and instead reach her by jumping. 
Unfortunately Fiona‘s stone is out of his jump range. Therefore Freddy considers to use other stones as intermediate stops and reach her by a sequence of several small jumps. 
To execute a given sequence of jumps, a frog‘s jump range obviously must be at least as long as the longest jump occuring in the sequence. 
The frog distance (humans also call it minimax distance) between two stones therefore is defined as the minimum necessary jump range over all possible paths between the two stones. 

You are given the coordinates of Freddy‘s stone, Fiona‘s stone and all other stones in the lake. Your job is to compute the frog distance between Freddy‘s and Fiona‘s stone. 

Input

The input will contain one or more test cases. The first line of each test case will contain the number of stones n (2<=n<=200). The next n lines each contain two integers xi,yi (0 <= xi,yi <= 1000) representing the coordinates of stone #i. Stone #1 is Freddy‘s stone, stone #2 is Fiona‘s stone, the other n-2 stones are unoccupied. There‘s a blank line following each test case. Input is terminated by a value of zero (0) for n.

Output

For each test case, print a line saying "Scenario #x" and a line saying "Frog Distance = y" where x is replaced by the test case number (they are numbered from 1) and y is replaced by the appropriate real number, printed to three decimals. Put a blank line after each test case, even after the last one.

Sample Input

2
0 0
3 4

3
17 4
19 4
18 5

0

Sample Output

Scenario #1
Frog Distance = 5.000

Scenario #2
Frog Distance = 1.414

Source

Ulm Local 1997

题目大意

求两点之间可到达路径的最长边距离的最小值。

题解

二分答案可过

这里floyed变形

f[i][j]=min(f[i][j],max(f[i][k],f[k][j]))

代码

/* distance撞关键字嘤嘤嘤

*/ 
#include<iostream>
#include<cstring>
#include<cmath>
#include<cstdio>
using namespace std;

int n,kse;
double f[202][202],xi[202],yi[202];
double distan(int i,int j){
    return sqrt((xi[i]-xi[j])*(xi[i]-xi[j])+(yi[i]-yi[j])*(yi[i]-yi[j]));
}

int main(){
    while(scanf("%d",&n)!=EOF){
        if(!n)break;
        memset(f,0x3f,sizeof(f));
        for(int i=1;i<=n;i++){
            scanf("%lf%lf",xi[i],yi[i]);
        //    cin>>xi[i]>>yi[i];
            f[i][i]=0;
        }
        for(int i=1;i<=n;i++)
            for(int j=i+1;j<=n;j++)
                f[i][j]=f[j][i]=distan(i,j);
        for(int k=1;k<=n;k++)
          for(int i=1;i<=n;i++)
            for(int j=1;j<=n;j++)
              f[i][j]=min(f[i][j],max(f[i][k],f[k][j]));
        printf("Scenario #%d\n",++kse);
        printf("Frog Distance = %.3f\n\n",f[1][2]);
    }
    return 0;
}

double输出时最好用%f 这个题%lf 会WA