poj 1328 Radar Installation
来源:互联网 发布:失忆知乎 编辑:程序博客网 时间:2024/06/05 11:11
Radar Installation
Time Limit: 1000MS Memory Limit: 10000KTotal Submissions: 48743 Accepted: 10884
Description
Assume the coasting is an infinite straight line. Land is in one side of coasting, sea in the other. Each small island is a point locating in the sea side. And any radar installation, locating on the coasting, can only cover d distance, so an island in the sea can be covered by a radius installation, if the distance between them is at most d.
We use Cartesian coordinate system, defining the coasting is the x-axis. The sea side is above x-axis, and the land side below. Given the position of each island in the sea, and given the distance of the coverage of the radar installation, your task is to write a program to find the minimal number of radar installations to cover all the islands. Note that the position of an island is represented by its x-y coordinates.
Figure A Sample Input of Radar Installations
We use Cartesian coordinate system, defining the coasting is the x-axis. The sea side is above x-axis, and the land side below. Given the position of each island in the sea, and given the distance of the coverage of the radar installation, your task is to write a program to find the minimal number of radar installations to cover all the islands. Note that the position of an island is represented by its x-y coordinates.
Figure A Sample Input of Radar Installations
Input
The input consists of several test cases. The first line of each case contains two integers n (1<=n<=1000) and d, where n is the number of islands in the sea and d is the distance of coverage of the radar installation. This is followed by n lines each containing two integers representing the coordinate of the position of each island. Then a blank line follows to separate the cases.
The input is terminated by a line containing pair of zeros
The input is terminated by a line containing pair of zeros
Output
For each test case output one line consisting of the test case number followed by the minimal number of radar installations needed. "-1" installation means no solution for that case.
Sample Input
3 21 2-3 12 11 20 20 0
Sample Output
Case 1: 2Case 2: 1
Source
Beijing 2002
Radar Installation
做的poj第一个题,题意就是在海岸上装最少的雷达(扫描半径为d)使其侦测到所有的小岛.
思路:求出小岛可以被扫描到的雷达的安装范围p[i].left,p[i].right,算完后对p排序,right大的在后面,若相同则left小的在后面。排完序后维持now_left就行了
代码:
#include<cstdio>#include<cmath>#include<algorithm>#include<iostream>using namespace std;struct pp{ double left; double right;}p[1005];double left(int x,int y,int d){ return x-sqrt(d*d-y*y);}double right(int x,int y,int d){ return x+sqrt(d*d-y*y);}bool cmp(pp p1,pp p2){ if(p1.right<p2.right) { return 1; } else { if(p1.right==p2.right) return p1.left>p2.left; } return 0;}int main(){ int n,d,Case=1;; while(scanf("%d%d",&n,&d)!=EOF) { if(!n&&!d)break; int i,ok=1;; for(i=0;i<n;i++) { int x,y; //cout<<"input"<<endl; scanf("%d%d",&x,&y); if(y>d) ok=0; if(ok) { p[i].left=left(x,y,d); p[i].right=right(x,y,d); } } //cout<<"ok"<<endl; if(!ok) { printf("Case %d: -1\n",Case++); continue; } sort(p,p+n,cmp); int count=1; double now_left=p[n-1].left; for(i=n-2;i>=0;i--) { if(p[i].right<now_left)//这个小岛不能被已安装的雷达扫到 { count+=1; now_left=p[i].left;//更新left } else { now_left=(now_left<p[i].left?p[i].left:now_left);//更新left } } printf("Case %d: %d\n",Case++,count); } return 0;}
0 0
- POJ 1328 "Radar Installation"
- POJ 1328 Radar Installation
- POJ 1328 Radar Installation
- POJ 1328 Radar Installation
- 1328 poj Radar Installation
- poj 1328 Radar Installation
- POJ 1328 Radar Installation
- poj 1328 Radar Installation
- poj 1328 Radar Installation
- POJ 1328 Radar Installation
- POJ 1328 Radar Installation
- POJ 1328 Radar Installation
- POJ 1328 Radar Installation
- POJ 1328 Radar Installation
- poj 1328 Radar Installation
- POJ-1328-Radar Installation
- poj 1328 Radar Installation
- POJ 1328 Radar Installation
- hive HQL笔记
- java.util.concurrent介绍
- codeforces 405 d toy sum
- UUID小记
- POJ2309 BST
- poj 1328 Radar Installation
- VMware中ubuntu忘记密码的解决办法
- QuickSort
- linux 下 svn用户权限
- CodeForces 405C Unusual Product
- string类(想要学好字符串,必须掌握string类)
- Java调用cmd命令 打开一个网站
- molu
- 编译器预定义宏__GNUC__和_MSC_VER