题目地址:http://poj.org/problem?id=1328 /* 贪心 (转载)题意:有一条海岸线,在海岸线上方是大海,海中有一些岛屿, 这些岛的位置已知,海岸线上有雷达,雷达的覆盖半径知道, 问最少需要多少个雷达覆盖所有的岛屿. (错误)思路:我开始是想从最左边的点雷达能探测的到的最右的位置出发,判断右边其余的点是否与该点距离小于d 是,岛屿数-1:不是,雷达数+1,继续... (正确)思路:每个岛屿的座标已知,以雷达半径为半径画圆,与x轴有两个交点. 也就是说,若要覆盖该岛,雷达…

POJ 1328 Radar Installation https://vjudge.net/problem/POJ-1328 题目: 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…

解题思路:给出n个岛屿,n个岛屿的坐标分别为(a1,b1),(a2,b2)-----(an,bn),雷达的覆盖半径为r 求所有的岛屿都被覆盖所需要的最少的雷达数目. 首先将岛屿坐标进行处理,因为雷达的位置在x轴上,所以我们设雷达的坐标为(x,0),对于任意一个岛屿p(a,b),因为岛屿要满足在雷达的覆盖范围内,所以 (x-a)^2+b^2=r^2,解得 xmin=a-sqrt(r*r-b*b);//即为区间的左端点 xmax=a+sqrt(r*r-b*b);//即为区间的右端点 接下来区间选点即…

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 li…

Radar Installation Time Limit: 1000MS   Memory Limit: 10000K Total Submissions: 54798   Accepted: 12352 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 loca…

Radar Installation Time Limit : 2000/1000ms (Java/Other)   Memory Limit : 20000/10000K (Java/Other) Total Submission(s) : 22   Accepted Submission(s) : 9 Problem Description Assume the coasting is an infinite straight line. Land is in one side of coa…

Radar Installation Time Limit: 1000MS   Memory Limit: 10000K Total Submissions: 106491   Accepted: 23648 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 loc…

Radar Installation Time Limit: 1000MS   Memory Limit: 10000K Total Submissions: 42925   Accepted: 9485 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 locat…

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, s…

POJ 1328 题意: 将一条海岸线看成X轴,X轴上面是大海,海上有若干岛屿,给出雷达的覆盖半径和岛屿的位置,要求在海岸线上建雷达,在雷达能够覆盖全部岛屿情况下,求雷达的最少使用量. 分析: 贪心法,先研究一下每个岛屿,设岛屿到海岸线的垂直距离为d,雷达的覆盖半径为k,若d>k,直接输出-1,若d<=k,则雷达的建造有一个活动区间[x1,x2](用平面几何可以求得出来).因此,在可以覆盖的情况下每个岛屿都有一个相应的活动区间.该问题也就转变成了最少区间选择问题即: 在n个区间中选择一个区间集…