Radar Installation 题目地址
Time Limit: 1000MS Memory Limit: 10000K Total Submissions: 86095 Accepted: 19253
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.
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
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 2 1 2 -3 1 2 1
1 2 0 2
0 0
Sample Output Case 1: 2 Case 2: 1
#include <iostream> #include <algorithm> #include <stdlib.h> #include <math.h> using namespace std; struct point { double left, right; }p[2010], temp; bool operator < (point a, point b) { return a.left < b.left; } int main() { int n; double r; int kase = 0; while (cin >> n >> r && (n || r)) { bool flag = false; for (int i = 0; i < n; i++) { double a, b; cin >> a >> b; if (fabs(b) > r) { flag = true; } else { p[i].left = a * 1.0 - sqrt(r * r - b * b); p[i].right = a * 1.0 + sqrt(r * r - b * b); } } cout << "Case " << ++kase << ": "; if (flag) { cout << -1 << endl; } else { int countt = 1; sort(p, p + n); temp = p[0]; for (int i = 1; i < n; i++) { if (p[i].left > temp.right) { countt++; temp = p[i]; } else if (p[i].right < temp.right) { temp = p[i]; } } cout << countt << endl; } } }