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计数方法,博弈论(扫描线,树形SG):HDU 5299 Circles Game
There are n circles on a infinitely large table.With every two circle, either one contains another or isolates from the other.They are never crossed nor tangent.
Alice and Bob are playing a game concerning these circles.They take turn to play,Alice goes first:
1、Pick out a certain circle A,then delete A and every circle that is inside of A.
2、Failling to find a deletable circle within one round will lost the game.
Now,Alice and Bob are both smart guys,who will win the game,output the winner‘s name.
Alice and Bob are playing a game concerning these circles.They take turn to play,Alice goes first:
1、Pick out a certain circle A,then delete A and every circle that is inside of A.
2、Failling to find a deletable circle within one round will lost the game.
Now,Alice and Bob are both smart guys,who will win the game,output the winner‘s name.
Input
The first line include a positive integer T<=20,indicating the total group number of the statistic.
As for the following T groups of statistic,the first line of every group must include a positive integer n to define the number of the circles.
And the following lines,each line consists of 3 integers x,y and r,stating the coordinate of the circle center and radius of the circle respectively.
n≤20000,|x|≤20000,|y|≤20000,r≤20000。
As for the following T groups of statistic,the first line of every group must include a positive integer n to define the number of the circles.
And the following lines,each line consists of 3 integers x,y and r,stating the coordinate of the circle center and radius of the circle respectively.
n≤20000,|x|≤20000,|y|≤20000,r≤20000。
Output
If Alice won,output “Alice”,else output “Bob”
Sample Input
2 1 0 0 1 6 -100 0 90 -50 0 1 -20 0 1 100 0 90 47 0 1 23 0 1
Sample Output
Alice Bob
这道题目可以说是模板题……
就是那个SG函数的求法貌似是结论,我不会证明。
1 #include <algorithm> 2 #include <iostream> 3 #include <cstring> 4 #include <cstdio> 5 #include <cmath> 6 #include <set> 7 using namespace std; 8 const int N=20010,M=40010; 9 int cnt,fir[N],to[N],nxt[N]; 10 void addedge(int a,int b){ 11 nxt[++cnt]=fir[a]; 12 to[fir[a]=cnt]=b; 13 } 14 int sqr(int x){return x*x;} 15 int tmp; 16 struct Circle{ 17 int x,y,r; 18 Circle(int _=0,int __=0,int ___=0){x=_;y=__;r=___;} 19 }c[N]; 20 21 struct Point{ 22 int x,id,tp; 23 Point(int _=0,int __=0,int ___=0){x=_;id=__;tp=___;} 24 friend bool operator<(Point a,Point b){ 25 double x=c[a.id].y+a.tp*sqrt(sqr(c[a.id].r)-sqr(tmp-c[a.id].x)); 26 double y=c[b.id].y+b.tp*sqrt(sqr(c[b.id].r)-sqr(tmp-c[b.id].x)); 27 if(x!=y)return x<y;return a.tp<b.tp; 28 } 29 }st[M]; 30 31 bool cmp(Point a,Point b){return a.x<b.x;} 32 set<Point>s;set<Point>::iterator it; 33 34 int fa[N],sg[N]; 35 int DFS(int x){ 36 sg[x]=0; 37 for(int i=fir[x];i;i=nxt[i]) 38 sg[x]^=DFS(to[i])+1; 39 return sg[x]; 40 } 41 42 void Init(){ 43 memset(fir,0,sizeof(fir)); 44 cnt=0; 45 } 46 int T,n; 47 int main(){ 48 scanf("%d",&T); 49 while(T--){ 50 Init();scanf("%d",&n); 51 for(int i=1;i<=n;i++){ 52 scanf("%d%d%d",&c[i].x,&c[i].y,&c[i].r); 53 st[2*i-1]=Point(c[i].x-c[i].r,i,-1); 54 st[2*i]=Point(c[i].x+c[i].r,i,1); 55 } 56 sort(st+1,st+2*n+1,cmp); 57 for(int i=1;i<=2*n;i++){ 58 Point x=st[i];tmp=x.x; 59 if(x.tp==-1){ 60 it=s.upper_bound(Point(0,x.id,1)); 61 if(it==s.end())addedge(fa[x.id]=0,x.id); 62 else{ 63 Point y=*it; 64 if(y.tp==1) 65 addedge(fa[x.id]=y.id,x.id); 66 else 67 addedge(fa[x.id]=fa[y.id],x.id); 68 } 69 s.insert(Point(0,x.id,1)); 70 s.insert(Point(0,x.id,-1)); 71 } 72 else{ 73 s.erase(Point(0,x.id,1)); 74 s.erase(Point(0,x.id,-1)); 75 } 76 } 77 printf(DFS(0)?"Alice\n":"Bob\n"); 78 } 79 return 0; 80 }
计数方法,博弈论(扫描线,树形SG):HDU 5299 Circles Game
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