题解

#include<bits/stdc++.h>
using namespace std;
double n,w,h;
double a[10001],b[10001];
void fsort(int l,int r){
	for(int i =0;i<=r;i++){
		for(int j = i+1;j<=r;j++){
			if(a[i] > a[j]){
				swap(a[i],a[j]);
				swap(b[i],b[j]);
			}else if(a[i] == a[j] && b[i] < b[j] ){
				swap(a[i],a[j]);
				swap(b[i],b[j]);
			}
		}
	}
}
int main(){
	int m;
	cin>> m;
	for(int i = 0;i<m;i++){
		int sum = 0,index=0;
		double x,r;
		cin>>n>>w>>h;
		for(int j = 0;j<n;j++){
			cin>>x>>r;
			if(2 * r > h){
				double xr = sqrt((double)(r*r - h*h/4));
				a[index] = x - xr>=0?x - xr:0;
				b[index] = x + xr;
				index++;
			}
		}
		fsort(0,index-1);
		double begin = a[0],end= b[0];
		if(begin <=0) sum++;
		int k =1;
		while(k<index && a[0]<=0){
			if(end>=w) break;
			if(k == index - 1){
				sum++;
				end=b[index-1];
				break;
			}
			if(end < a[k]) break;
			double max=end;
			while(end >= a[k]){
				max = max>b[k]?max:b[k];
				k++;
			}
			end=max;
			sum++;
		}
		if(end<w) sum=0;
		cout<<sum<<endl;
		
	}

	
	return 0;
}