delete pics to save space

7.1328.cpp

@@ -0,0 +1,33 @@
+#include<cstdio>
+#include<cmath>
+#include<algorithm>
+using namespace std;
+const int maxn=1005;
+int n,d,kase;
+struct Is { double L,R; };
+inline bool operator<(const Is &a,const Is &b) { return a.L<b.L; }
+Is isl[maxn];
+int main()
+{
+#ifdef local
+	freopen("pro.in","r",stdin);
+#endif
+	while(scanf("%d%d",&n,&d)==2&&!(n==0&&d==0))
+	{
+		bool flg=false;
+		for(int i=0;i<n;i++)
+		{
+			int x,y; scanf("%d%d",&x,&y);
+			if(y>d) flg=true;
+			double dt=sqrt(d*d-y*y);
+			isl[i]=(Is){x-dt,x+dt};
+		}
+		sort(isl,isl+n);
+		int res=0; double pos=-1e10;
+		for(int i=0;i<n;i++)
+			if(isl[i].L>pos) { res++; pos=isl[i].R; }
+			else pos=min(pos,isl[i].R);
+		printf("Case %d: %d\n",++kase,flg?-1:res);
+	}
+	return 0;
+}