第一种方法为自己写的，第二种方法为和队友讨论后改进。
附一句话：博客园是一个分享程序员知识的地方，我不明白，写的代码为啥就不算这个分享的知识呢，为什么老是移除什么首页，不符合规定，所谓云云。。
代码是程序员分享的一切的思想以及细节的终极体现形式。。。
如果有一个博客，都是代码，我反而高兴，终于那些繁琐的，具有二义性、甚至多义性的歧义的文字终于没有了，只剩下了简明、逻辑、有效的东西。。。
本来应该用c++写的，直接使用java写了，感觉更顺手。
Radar
时间限制：1000 ms | 内存限制：65535 KB
难度：3
- 描述
- 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.
- 输入
- 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 - 输出
- 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.
- 样例输入
-
3 2 1 2 -3 1 2 1 1 2 0 2 0 0
- 样例输出
-
Case 1: 2 Case 2: 1
1 import java.util.*; 2 public class Main { 3 public static void main(String args[]){ 4 Scanner cin=new Scanner(System.in); 5 int casenum=0; 6 while(cin.hasNext()){ 7 casenum++; 8 int n=cin.nextInt(); 9 int d=cin.nextInt(); 10 int radarNum=1; 11 12 if(n==0&&d==0) break; 13 if(d<=0) {System.out.println("Case "+casenum+": -1");} 14 15 16 Xy a[]=new Xy[n]; 17 18 boolean slove=true; 19 20 for(int i=0;i<n;i++){ 21 22 int x=cin.nextInt(); 23 int y=cin.nextInt(); 24 25 if(y>d) slove=false; 26 if(d>0&&slove){ 27 a[i]=new Xy(); 28 a[i].min=x-Math.sqrt(d*d-y*y); 29 a[i].max=x+Math.sqrt(d*d-y*y); 30 } 31 } 32 33 if(d>0){ 34 if(n==1&&slove) radarNum=1; 35 if(n>1&&slove){ 36 for(int i=0;i<n;i++) 37 for(int j=i+1;j<n;j++) 38 if(a[i].min>a[j].min){ 39 Xy tmp=a[i]; 40 a[i]=a[j]; 41 a[j]=tmp; 42 } 43 double minRadar=a[0].min; 44 double maxRadar=a[0].max; 45 double right=a[0].max; 46 47 for(int i=1;i<n;i++){ 48 49 if(a[i].max<right){ 50 right=a[i].max; 51 }else 52 if(right<a[i].min){ 53 right=a[i].max; 54 radarNum++; 55 } 56 57 58 } 59 } 60 System.out.println("Case "+casenum+": "+radarNum); 61 62 } 63 } 64 } 65 66 67 } 68 69 class Xy { 70 71 double min=0; 72 double max=0; 73 public Xy(){ 74 75 } 76 public Xy(int min,int max){ 77 this.min=min; 78 this.max=max; 79 } 80 81 }
第二种AC方法：
1 import java.util.*; 2 public class Main { 3 public static void main(String args[]){ 4 Scanner cin=new Scanner(System.in); 5 int casenum=0; 6 while(cin.hasNext()){ 7 casenum++; 8 int n=cin.nextInt(); 9 int d=cin.nextInt(); 10 int radarNum=1; 11 12 if(n==0&&d==0) break; 13 if(d<=0) {System.out.println("Case "+casenum+": -1");} 14 15 16 Xy a[]=new Xy[n]; 17 18 boolean slove=true; 19 20 for(int i=0;i<n;i++){ 21 22 int x=cin.nextInt(); 23 int y=cin.nextInt(); 24 25 if(y>d) slove=false; 26 if(d>0&&slove){ 27 a[i]=new Xy(); 28 a[i].min=x-Math.sqrt(d*d-y*y); 29 a[i].max=x+Math.sqrt(d*d-y*y); 30 } 31 } 32 33 if(d>0){ 34 if(n==1&&slove) radarNum=1; 35 if(n>1&&slove){ 36 for(int i=0;i<n;i++) 37 for(int j=i+1;j<n;j++) 38 if(a[i].min>a[j].min){ 39 Xy tmp=a[i]; 40 a[i]=a[j]; 41 a[j]=tmp; 42 } 43 double minRadar=a[0].min; 44 double maxRadar=a[0].max; 45 46 47 for(int i=1;i<n;i++){ 48 if(a[i].min>maxRadar) { 49 radarNum++; 50 minRadar=a[i].min; 51 maxRadar=a[i].max; 52 }else{ 53 if(a[i].max>maxRadar) 54 minRadar=a[i].min; 55 else{ 56 minRadar=a[i].min; 57 maxRadar=a[i].max; 58 } 59 } 60 61 62 } 63 } 64 System.out.println("Case "+casenum+": "+radarNum); 65 66 } 67 } 68 } 69 70 71 } 72 73 class Xy { 74 75 double min=0; 76 double max=0; 77 public Xy(){ 78 79 } 80 public Xy(int min,int max){ 81 this.min=min; 82 this.max=max; 83 } 84 85 }