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POJ 3335 Rotating Scoreboard
题目大意:同 POJ3130
解题思路:同 POJ3130
POJ3130解题报告:点此进入
注意:两个题给出点的顺序不一样。不要老是抄模版(我不会告诉你我就是这么做的)。
下面是代码:
#include <set> #include <map> #include <queue> #include <math.h> #include <vector> #include <string> #include <stdio.h> #include <string.h> #include <stdlib.h> #include <iostream> #include <algorithm> #define eps 1e-8 #define pi acos(-1.0) #define inf 107374182 #define inf64 1152921504606846976 #define lc l,m,tr<<1 #define rc m + 1,r,tr<<1|1 #define zero(a) fabs(a)<eps #define iabs(x) ((x) > 0 ? (x) : -(x)) #define clear1(A, X, SIZE) memset(A, X, sizeof(A[0]) * (SIZE)) #define clearall(A, X) memset(A, X, sizeof(A)) #define memcopy1(A , X, SIZE) memcpy(A , X ,sizeof(X[0])*(SIZE)) #define memcopyall(A, X) memcpy(A , X ,sizeof(X)) #define max( x, y ) ( ((x) > (y)) ? (x) : (y) ) #define min( x, y ) ( ((x) < (y)) ? (x) : (y) ) using namespace std; const int maxn = 55; int dq[maxn], top, bot, pn, order[maxn], ln; struct Point { double x, y; } p[maxn]; struct Line { Point a, b; double angle; } l[maxn]; int dblcmp(double k) { if(fabs(k) < eps) return 0; return k > 0 ? 1 : -1; } double multi(Point p0, Point p1, Point p2) { return (p1.x-p0.x)*(p2.y-p0.y) - (p1.y-p0.y)*(p2.x-p0.x); } bool cmp(int u, int v) { int d = dblcmp(l[u].angle-l[v].angle); if(!d) return dblcmp(multi(l[u].a, l[v].a, l[v].b)) < 0; //大于0取向量左半部分为半平面,小于0,取右半部分 return d < 0; } void getIntersect(Line l1, Line l2, Point& p) { double dot1, dot2; dot1 = multi(l2.a, l1.b, l1.a); dot2 = multi(l1.b, l2.b, l1.a); p.x = (l2.a.x * dot2 + l2.b.x * dot1) / (dot2 + dot1); p.y = (l2.a.y * dot2 + l2.b.y * dot1) / (dot2 + dot1); } bool judge(Line l0, Line l1, Line l2) { Point p; getIntersect(l1, l2, p); return dblcmp(multi(p, l0.a, l0.b)) > 0; //大于小于符号与上面cmp()中注释处相反 } void addLine(double x1, double y1, double x2, double y2) { l[ln].a.x = x1; l[ln].a.y = y1; l[ln].b.x = x2; l[ln].b.y = y2; l[ln].angle = atan2(y2-y1, x2-x1); order[ln] = ln; ln++; } void halfPlaneIntersection() { int i, j; sort(order, order+ln, cmp); for(i = 1, j = 0; i < ln; i++) if(dblcmp(l[order[i]].angle-l[order[j]].angle) > 0) order[++j] = order[i]; ln = j + 1; dq[0] = order[0]; dq[1] = order[1]; bot = 0; top = 1; for(i = 2; i < ln; i++) { while(bot < top && judge(l[order[i]], l[dq[top-1]], l[dq[top]])) top--; while(bot < top && judge(l[order[i]], l[dq[bot+1]], l[dq[bot]])) bot++; dq[++top] = order[i]; } while(bot < top && judge(l[dq[bot]], l[dq[top-1]], l[dq[top]])) top--; while(bot < top && judge(l[dq[top]], l[dq[bot+1]], l[dq[bot]])) bot++; } bool isThereACore() { if(top-bot > 1) return true; return false; } int main() { int i,T; scanf("%d",&T); while( T--) { scanf ("%d", &pn); for(i = 0; i < pn; i++) scanf ("%lf%lf", &p[i].x, &p[i].y); for(ln = i = 0; i < pn-1; i++) addLine(p[i].x, p[i].y, p[i+1].x, p[i+1].y); addLine(p[i].x, p[i].y, p[0].x, p[0].y); halfPlaneIntersection(); if(isThereACore()) printf ("YES\n"); else printf ("NO\n"); } return 0; }
POJ 3335 Rotating Scoreboard
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