习题8-11(uva-1615)

#include <iostream>
#include <istream>
#include <sstream>
#include <vector>
#include <stack>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <queue>
#include <cstring>
#include <unordered_map>
#include <unordered_set>
#include <algorithm>
#include <numeric>
#include <chrono>
#include <ctime>
#include <cmath>
#include <cctype>
#include <string>
#include <cstdio>
#include <iomanip>


#include <thread>
#include <mutex>
#include <condition_variable>
#include <functional>
#include <iterator>
using namespace std;
const int maxn = 1e5 + 7;
int l, n, d;
struct Node
{
    
    
	double l, r;
	bool operator<(const Node& input) {
    
    
		if (l == input.l) return r < input.r;
		return l < input.l;
	}
}nodes[maxn];

int GetResult()
{
    
    
	int ret = 1;
	double last = nodes[0].r;
	for (int i = 0; i < n; i++) {
    
    
		if (nodes[i].l > last) {
    
    
			last = nodes[i].r;
			ret++;
		}
	}
	return ret;
}
int main()
{
    
    
	while (cin >> l >> d >> n) {
    
    
		int x,y,w,d2 = d * d;
		for (int i = 0; i < n; i++) {
    
    
			cin >> x >> y;
			w = sqrt(d2 - y * y);
			nodes[i].l = x - w;
			nodes[i].r = x + w;
		}
		sort(nodes, nodes + n);
		cout << GetResult() << endl;
	}
	return 0;
}