比较基础的贪心
设计知识：勾股定理+贪心
预计难度：上位黄/绿
CSP-S复赛前发题解 rp++

#include <bits/stdc++.h>
using namespace std;
#define int long long
double T, n, L, W;
bool check(double bp,double pos,double r)
{
	if(r<(W/2)) return false;
	double d=sqrt(r*r-(W/2)*(W/2));
	return (pos-d)<=bp;
}
double cal(double pos,double r)
{
	double d=sqrt(r*r-(W/2)*(W/2));
	return pos+d;
}
struct Poi{
	double pos,r;
	friend bool operator<(Poi a,Poi b){
		return cal(a.pos,a.r)<cal(b.pos,b.r);
	}
};
signed main() {
    ios::sync_with_stdio(0);
    cin.tie(nullptr), cout.tie(nullptr);
    cin >> T;
    while (T--) {
        cin >> n >> L >> W;
		vector<Poi> vec(n+1);
		for(int i=1;i<=n;i++){
			cin>>vec[i].pos>>vec[i].r;
		}
		sort(vec.begin()+1,vec.end());
		double l=0,r=L;
		int cnt=0;
		while(l<r)
		{
			double rm=0;
			for(int i=1;i<=n;i++)
				if(check(l,vec[i].pos,vec[i].r))
					rm=max(cal(vec[i].pos,vec[i].r),rm);
			if(rm>l) l=rm;
			else {
				cnt=-1;
				break;
			}
			cnt++;
		}
		cout<<cnt<<endl;
    }
    return 0;
}