UVALive - 2519 Radar Installation

题目大意：给出 n 和半径 r， 然后给出 n 个坐标， 现在要求在 x 轴选出最少的点， 以这些点为圆心， 半径为 r 画圆， 要求将所有点均在画的圆内

解题思路：区间选点问题

#include <cstdio>#include <algorithm>#include <cmath>using namespace std;struct Node {double l;double r;} A[1005];int cmp (Node a, Node b) {return a.r < b.r;};int main() {int n, d, T = 0;while (scanf("%d%d", &n, &d), n) {printf("Case %d: ", ++T);int x, y, flag = 1;for (int i = 0; i < n; i++) {scanf("%d%d", &x, &y);if (y > d) {flag = 0;break;}double t = sqrt(d*d - y*y);A[i].l = x - t;A[i].r = x + t;}sort(A, A + n, cmp);int cnt = 1;double temp = A[0].r;for (int i = 1; i < n; i++) {if (A[i].l - temp <= 1e-4)continue;temp = A[i].r;cnt++;}flag ? printf("%d\n", cnt) : printf("-1\n");}return 0;}