地雷阵 参考代码

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

typedef long long LL;
const double PI = acos(-1.0);
const int maxn = 100000 + 100;
struct Node {
    double l, r;
    Node() {}
    Node(double l, double r): l(l), r(r) {}
};

bool operator<(const Node &a, const Node &b) {
    return a.l < b.l;
}

int n;
LL x, y, r;
double k, sum, ll, rr, theta1, theta2;
Node node[maxn];

int main() {
#ifdef ExRoc
    freopen("test.txt", "r", stdin);
#endif // ExRoc
    ios::sync_with_stdio(false);

    cin >> n;
    for (int i = 0; i < n; ++i) {
        cin >> x >> y >> r;
        double theta = asin(r / sqrt(x * x + y * y));
        double beta = atan(y * 1.0 / x);
        node[i] = Node(beta - theta, beta + theta);
    }
    sort(node, node + n);
    for (int i = 0; i < n; ++i) {
        if (rr < node[i].l) {
            sum += rr - ll;
            rr = node[i].r;
            ll = node[i].l;
        } else {
            rr = max(node[i].r, rr);
        }
    }
    sum += rr - ll;
    printf("%.3lf\n", 1 - sum / (PI / 2));

    return 0;
}