(贪心咯)

千万记得要double ，否则会错的

C++ 代码

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int maxn= 50100;
struct node
{
    double l, r;
}a[maxn];
int d, n;
bool cmp(node a, node b)
{
    return a.r < b.r;
}
int main()
{
    scanf("%d%d",&n,&d);
    for(int i = 1; i <= n; i ++)
    {
        double x, y;
        scanf("%lf%lf",&x,&y);
        if(y > d)
        {
            printf("-1\n");
            return 0;
        }
        a[i].l = x-sqrt(d*d-y*y);
        a[i].r = x+sqrt(d*d-y*y);
    }
    int num = 1;
    sort(a+1,a+1+n,cmp);
    double q = a[1].r;
    for(int i = 2; i <= n; i ++)
    {
        if(a[i].l <= q)
        continue;
        else
        {
            num ++;
            q = a[i].r;
        }
    }
    printf("%d\n",num);
    return 0;
}