记录编号	570841	评测结果	AAAAAA
题目名称	喷水装置	最终得分	100
用户昵称	lihaoze	是否通过	通过
代码语言	C++	运行时间	0.057 s
提交时间	2022-04-20 19:55:59	内存使用	3.03 MiB

#include <bits/stdc++.h>
#define OPEN(x) freopen(#x".in", "r", stdin); freopen(#x".out", "w", stdout)
#define fi first
#define se second

using PDD = std::pair<double, double>;

int main() {
    OPEN(sprinkler);
    int t; std::cin >> t;
    int n;
    double l, w;
    while (~scanf("%d%lf%lf", &n, &l, &w)) {
        w /= 2;
        std::vector<PDD> q;
        for (int i = 1; i <= n; ++ i) {
            double a, b;
            scanf("%lf%lf", &a, &b);
            if (b > w) {
                double f = sqrt(b * b - w * w);
                q.emplace_back(a - f, a + f);
            }
        }
        std::sort(q.begin(), q.end(), [&](PDD x, PDD y) { return x.fi < y.fi; });
        int len = q.size();
        int flag = 0, ans = 0;
        double st = 0, ed = l;
        for (int i = 0; i < len; ++ i) {
            int j = i; double res = -1e9;
            while (j < len && q[j].fi <= st) 
                res = std::max(res, q[j++].se);
            if (res <= st) break;
            ++ ans;
            if (res >= ed) {
                flag = 1;
                break;
            }
            st = res; 
            i = j - 1;
        }
        if (flag) printf("%d\n", ans);
        else puts("-1");
    }
    return 0;
}