mirror of
https://github.com/Kiritow/OJ-Problems-Source.git
synced 2024-03-22 13:11:29 +08:00
66 lines
1.9 KiB
C++
66 lines
1.9 KiB
C++
#include<stdio.h>
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#include<string.h>
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#include<stdlib.h>
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#include<math.h>
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#include<algorithm>
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const int maxn = 2111;
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const double eps = 1e-8;
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const double pi = acos(-1.0);
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int n, R, ctp;
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inline int dcmp(double x) {return (x > eps) - (x < -eps);}
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inline double Sqr(double x){return x * x;}
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struct Point {int x, y;} p[maxn];
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inline double CalDis(const Point &a, const Point &b)
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{return sqrt(Sqr(a.x - b.x) + Sqr(a.y - b.y));}
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struct Cov { double site; int se;}cover[maxn <<2];
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int AScomp(const void *a, const void *b)
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{
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if(!dcmp((*(Cov*)a).site - (*(Cov*)b).site))
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return -((*(Cov*)a).se - (*(Cov*)b).se);
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return dcmp((*(Cov*)a).site - (*(Cov*)b).site);
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}
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void AngManage(double &x)
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{
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while(x + pi < eps) x += 2 * pi;
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while(x - pi > eps) x -= 2 * pi;
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}
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void AddAnSeg(double start, double end)
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{
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AngManage(start), AngManage(end);
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if(start - end > eps) AddAnSeg(start, pi), AddAnSeg(-pi + eps * 2, end);
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else
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{
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cover[ctp].site = start, cover[ctp].se = 1;++ ctp;
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cover[ctp].site = end, cover[ctp].se = -1;++ ctp;
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}
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}
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int MakeAns()
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{
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int i, j, ans = 0, cnt;
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double dis, ang, ac, RR = 2 * (R + 0.001);
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for(i = 0 ; i < n; ++ i)
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{
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for(j = ctp = 0; j < n; ++ j)
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if(j != i && (dis = CalDis(p[i], p[j])) < RR)
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{
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ang = atan2((double)p[j].y - p[i].y, (double)p[j].x - p[i].x);
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ac = acos(dis * 0.5 / R);
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AddAnSeg(ang - ac, ang + ac);
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}
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qsort(cover, ctp, sizeof(Cov), AScomp);
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for(j = cnt = 0; j < ctp; ++ j)
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ans = std::max(ans, cnt += cover[j].se);
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}
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return ans + 1;
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}
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int main()
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{
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while(scanf("%d%d", &n, &R), n | R)
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{
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for(int i = 0; i < n; ++ i)
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scanf("%d%d", &p[i].x, &p[i].y);
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printf("It is possible to cover %d points.\n", MakeAns());
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}
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return 0;
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}
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