Zoj address: http://acm.zju.edu.cn/onlinejudge/showProblem.do? Problemid = 360
Poj address: http://poj.org/problem? Id = 1328
Solution: greedy
1 # include <stdio. h>
2 # include <string. h>
3 # include <stdlib. h>
4 # include <math. h>
5
6 struct P {
7 Double X, Y, left, right;
8} p [1010];
9
10 int CMP (const void * a, const void * B ){
11 struct p * c = (struct p *);
12 struct p * D = (struct p *) B;
13 return C-> left> D-> left? 1:-1;
14}
15
16 int main (){
17 int N, I, j, R, ANS, lose, Case = 1;
18 double D, X, DIS, high;
19 while (scanf ("% d", & N, & R )! = EOF ){
20 if (n = 0 & R = 0 ){
21 break;
22}
23 lose = 0;
24 d = (double) R;
25 For (I = 0; I <n; I ++ ){
26 scanf ("% lf", & P [I]. X, & P [I]. y );
27 if (P [I]. Y> d) {// If the left side of Y at a point is greater than the radar radius, it cannot be overwritten.
28 lose = 1;
29}
30 Dis = SQRT (D * D-P [I]. y * P [I]. y );
31 P [I]. Left = P [I]. X-DIS;
32 P [I]. Right = P [I]. x + DIS;
33}
34 if (lose = 1 ){
35 printf ("case % d:-1 \ n", Case ++ );
36 continue;
37}
38 qsort (p, N, sizeof (P [0]), CMP );
39 ans = 1;
40 high = P [0]. Right; // set the right endpoint of the first vertex to the farthest vertex.
41 for (I = 1; I <n; I ++ ){
42 if (P [I]. Left <= high ){
43 high = P [I]. Right <High? P [I]. Right: high; // If the left endpoint of the vertex is within the farthest vertex, update the farthest vertex.
44}
45 else {// If the left endpoint is not within the farthest point, the number of radars + 1 will update the farthest point
46 ans ++;
47 high = P [I]. Right;
48}
49}
50 printf ("case % d: % d \ n", Case ++, ANS );
51}
52 return 0;
53}
ZOJ-1360 | POJ-1328 -- radar installation
