牛客竞赛 1020 最大半径的圆

学习使用bitset , 记录所有和点相连的点

代码

#include<bits/stdc++.h>
using namespace std;

inline int read() {
    int ans = 0, f = 1;
    char ch = getchar();
    while (ch < '0' || ch > '9') {
        if (ch == '-')f = -1;
        ch = getchar();
    }
    while (ch <= '9' && ch >= '0') {
        ans = ans * 10 + ch - '0';
        ch = getchar();
    }
    return ans * f;
}
const int N = 3005;
double x[N],y[N];
bitset<N> p[N];
struct Item {
    double dis;
    int l,r;
    bool operator<(const Item &x) const {
        return dis > x.dis;
    }
};
vector<Item> v;
double getdis(double x1,double y1,double x2,double y2) {
    return (x1-x2) * (x1-x2) + (y1-y2) * (y1-y2);
}
int main() {
    int n =read();
    for (int i = 1; i<= n; i++) {
        x[i]=read(),y[i]=read();
    }


    for (int i =1; i<= n; i++) {
        for (int j = i+1;j<=n;j++) {
            v.push_back({getdis(x[i],y[i],x[j],y[j]),i,j});
        }
    }
    sort(v.begin(),v.end());
    for (auto e : v) {
        if ((p[e.l] & p[e.r]) !=0) {
            cout<<fixed<<setprecision(8)<<sqrt(e.dis)/2.0<<"\n";
            return 0;
        }
        p[e.l][e.r]= true;
        p[e.r][e.l] = true;
    }


    return 0;
}