POJ-2253 Frogger（最短路）

#include<iostream>
#include<cmath>
#include<cstring>
#include<queue>
#include<vector>
#include<cstdio>
#include<algorithm>
#include<map>
#include<set>
#define rep(i,e) for(int i=0;i<(e);i++)
#define rep1(i,e) for(int i=1;i<=(e);i++)
#define repx(i,x,e) for(int i=(x);i<=(e);i++)
#define X first
#define Y second
#define PB push_back
#define MP make_pair
#define mset(var,val) memset(var,val,sizeof(var))
#define scd(a) scanf("%d",&a)
#define scdd(a,b) scanf("%d%d",&a,&b)
#define scddd(a,b,c) scanf("%d%d%d",&a,&b,&c)
#define pd(a) printf("%d\n",a)
#define scl(a) scanf("%lld",&a)
#define scll(a,b) scanf("%lld%lld",&a,&b)
#define sclll(a,b,c) scanf("%lld%lld%lld",&a,&b,&c)
#define IOS ios::sync_with_stdio(false);cin.tie(0)

using namespace std;
typedef long long ll;
template <class T>
void test(T a){cout<<a<<endl;}
template <class T,class T2>
void test(T a,T2 b){cout<<a<<" "<<b<<endl;}
template <class T,class T2,class T3>
void test(T a,T2 b,T3 c){cout<<a<<" "<<b<<" "<<c<<endl;}
template <class T>
inline bool scan_d(T &ret){
    char c;int sgn;
    if(c=getchar(),c==EOF) return 0;
    while(c!=‘-‘&&(c<‘0‘||c>‘9‘)) c=getchar();
    sgn=(c==‘-‘)?-1:1;
    ret=(c==‘-‘)?0:(c-‘0‘);
    while(c=getchar(),c>=‘0‘&&c<=‘9‘) ret = ret*10+(c-‘0‘);
    ret*=sgn;
    return 1;
}
const int N = 1e6+10;
const int inf = 0x3f3f3f3f;
const ll INF = 0x3f3f3f3f3f3f3f3fll;
const ll mod = 1000000000;
int T;

void testcase(){
    printf("Case %d:",++T);
}

const int MAXN = 5e5+10 ;
const int MAXM = 250;
const double eps = 1e-8;
const double PI = acos(-1.0);

struct point{
    int x,y;
}node[MAXM];

double w[MAXM][MAXM],dis[MAXM];
int n;
int vis[MAXM];

double dist(point a,point b){
    return sqrt(1.0*(a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));
}

void init(){
    for(int i=1;i<=n;i++) scanf("%d%d",&node[i].x,&node[i].y);
    for(int i=1;i<=n;i++)
        for(int j=1;j<=n;j++)
            w[i][j]=dist(node[i],node[j]);
}
void dijkstra(){
    mset(vis,0);
    for(int i=1;i<=n;i++) dis[i]=inf;
    dis[1]=0;
    for(int i=1;i<=n;i++){
        int pos,m=inf;
        for(int j=1;j<=n;j++){
            if(!vis[j]&&dis[j]<m){
                pos=j;
                m=dis[j];
            }
        }
        vis[pos]=1;
        for(int j=1;j<=n;j++){
            dis[j]=min(dis[j],max(dis[pos],w[pos][j]));
        }
    }
}
int main() {

    int t=0;
    while(~scanf("%d",&n)&&n){
        init();
        dijkstra();
        if(t) puts("");
        printf("Scenario #%d\nFrog Distance = %.3f\n", ++t, dis[2]);
    }
    return 0;
}