138 lines
3.4 KiB
C++
138 lines
3.4 KiB
C++
#include <cstdio>
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#include <cstdlib>
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#include <cmath>
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#include <algorithm>
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using namespace std;
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const int maxn = 100;
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const double eps = 1e-3;
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const int times = 5;
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const double INF = 99999999;
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int n;
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struct point
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{
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double x, y, r;
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} p[maxn], test[maxn];
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inline int dblcmp( double x )
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{
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if( fabs(x) < eps )
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return 0;
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return x > 0 ? 1 : -1;
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}
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inline double sqr( double x )
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{
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return x*x;
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}
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double dis( point& aa, point& bb )
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{
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return sqrt(sqr(aa.x-bb.x)+sqr(aa.y-bb.y));
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}
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double cross( point& k, point& aa, point& bb )
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{
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return (k.x-aa.x)*(k.y-bb.y)-(k.y-aa.y)*(k.x-bb.x);
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}
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double seg_point_dis( point& l1, point& l2, point& k )
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{
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double a, b, c;
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a = dis(l1, k);
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b = dis(l2, k);
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c = dis(l1, l2);
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if( dblcmp(a*a+c*c-b*b) < 0 )
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return a;
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else if( dblcmp(b*b+c*c-a*a) < 0 )
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return b;
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else
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return fabs(cross(k, l1, l2)/c);
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}
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bool point_inside( point& aa )
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{
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int i, cnt = 0;
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double t;
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for( i = 0; i < n; ++i )
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{
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if( (p[i].y <= aa.y && p[i+1].y > aa.y) ||
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(p[i+1].y <= aa.y && p[i].y > aa.y) )
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{
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if( !dblcmp(p[i].y-p[i+1].y) )
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{
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if( dblcmp(p[i].y-aa.y) == 0 )
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cnt++;
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t = -INF;
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}
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else
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t = p[i+1].x - (p[i+1].x-p[i].x)*(p[i+1].y-aa.y)/(p[i+1].y-p[i].y);
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if( dblcmp( t - aa.x ) >= 0 )
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cnt++;
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}
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}
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return cnt%2;
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}
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void cal( point& aa )
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{
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double t;
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aa.r = INF;
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for( int i = 0; i < n; ++i )
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{
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t = seg_point_dis(p[i], p[i+1], aa);
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aa.r = min(aa.r, t);
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}
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}
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int main()
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{
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int i, j;
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double R, delte, maxx, maxy, minx, miny, ang;
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point temp;
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bool ok;
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while( scanf("%d", &n), n )
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{
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ok = 0;
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maxx = maxy = 0;
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minx = miny = INF;
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for( i = 0; i < n; ++i )
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{
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scanf("%lf %lf", &p[i].x, &p[i].y);
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maxx = max(maxx, p[i].x);
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maxy = max(maxy, p[i].y);
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minx = min(minx, p[i].x);
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miny = min(miny, p[i].y);
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}
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p[n] = p[0];
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for( i = 0; i < n; ++i )
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{
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test[i].x = (p[i].x+p[i+1].x)/2;
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test[i].y = (p[i].y+p[i+1].y)/2;
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test[i].r = 0;
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}
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scanf("%lf", &R);
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maxx -= minx; maxy -= miny;
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delte = sqrt(maxx*maxx+maxy*maxy)/2;
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while( !ok && delte > eps )
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{
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for( i = 0; !ok && i < n; ++i )
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{
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for( j = 0; !ok && j < times; ++j )
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{
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ang = rand();
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temp.x = test[i].x + delte*cos(ang);
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temp.y = test[i].y + delte*sin(ang);
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if( point_inside(temp) )
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{
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cal(temp);
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if( temp.r > test[i].r )
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{
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test[i] = temp;
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if( dblcmp(temp.r-R) >= 0 )
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ok = 1;
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}
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}
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}
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}
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delte *= 0.90;
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}
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if( ok )
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printf("Yes\n");
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else
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printf("No\n");
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}
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return 0;
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}
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