97 lines
2.6 KiB
C++
97 lines
2.6 KiB
C++
#include <cstdio>
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#include <cstring>
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#include <cmath>
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#define MAXN 210
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#define EPS 1e-3
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using namespace std;
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int n;
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struct Edge{
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int v,next;
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Edge(){}
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Edge(int _v,int _next):v(_v),next(_next){}
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}edge[MAXN*MAXN];
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int head[MAXN], size;
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inline void initial(){
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memset(head,-1,sizeof(int)*(n+2));
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size = 0;
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}
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inline void add_edge(int u,int v){
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edge[size] = Edge(v,head[u]);
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head[u] = size ++;
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}
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int belong[MAXN];
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bool vis[MAXN];
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int depth;
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int bcnt;
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int dfn[MAXN], low[MAXN];
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int stack[MAXN], tail ;
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inline void Tarjan(int u){
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dfn[u] = low[u] = depth ++;
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vis[u] = 1;
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stack[++tail] = u;
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for(int i = head[u];i != -1;i = edge[i].next){
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int v = edge[i].v;
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if(dfn[v] == -1){
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Tarjan(v);
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if(low[u] > low[v])
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low[u] = low[v];
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}else if(vis[v] && low[u] > dfn[v]){
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low[u] = dfn[v];
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}
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}
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if(low[u] == dfn[u]){
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bcnt ++;
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int j;
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do{
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j = stack[tail--];
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vis[j] = 0;
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belong[j] = bcnt;
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}while(j != u);
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}
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}
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double x[MAXN], y[MAXN];
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inline double Cal(int i,int j){
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return (x[i]-x[j])*(x[i]-x[j]) + (y[i]-y[j])*(y[i]-y[j]);
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}
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inline bool can(){
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int N = n/2;
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for(int i = 1;i <= N; ++i)
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if(belong[i] == belong[i+N]) return false;
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return true;
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}
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int main()
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{
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int N;
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while(scanf("%d",&N) != EOF){
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n = 2*N;
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for(int i = 1;i <= N; ++i)
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scanf("%lf%lf%lf%lf",&x[i],&y[i],&x[i+N],&y[i+N]);
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double right = 10000.0*10000.0, left = 0.0, mid;
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while(right - left >= EPS){
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mid = (right + left)/2.0;
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initial();
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for(int i = 1;i < n; ++i)
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for(int j = i + 1;j <= n; ++j){
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if(Cal(i,j) < mid){
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int u, v;
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if(i <= N) u = i + N;
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else u = i - N;
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if(j <= N) v = j + N;
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else v = j - N;
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add_edge(i,v);
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add_edge(j,u);
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}
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}
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tail = depth = bcnt = 0;
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memset(vis,0,sizeof(bool)*(n+2));
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memset(dfn,-1,sizeof(int)*(n+2));
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memset(low,0,sizeof(int)*(n+2));
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for(int i = 1;i <= n; ++i)
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if(dfn[i] == -1) Tarjan(i);
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if(can()) left = mid;
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else right = mid;
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}
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printf("%.2lf\n",sqrt(left)/2.0);
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}
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}
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