【BZOJ】1419 Red is Good
2017-03-21 09:11
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大意:
桌面上有R张红牌和B张黑牌,随机打乱顺序后放在桌面上,开始一张一张地翻牌,翻到红牌得到1美元,黑牌则付出1美元。可以随时停止翻牌,在最优策略下平均能得到多少钱
直接期望DP
f[i][j]表示开一局i红j黑的游戏的期望收益,然后f[i][j]可以由f[i-1][j]和f[i][j-1]转移
要滚动
桌面上有R张红牌和B张黑牌,随机打乱顺序后放在桌面上,开始一张一张地翻牌,翻到红牌得到1美元,黑牌则付出1美元。可以随时停止翻牌,在最优策略下平均能得到多少钱
直接期望DP
f[i][j]表示开一局i红j黑的游戏的期望收益,然后f[i][j]可以由f[i-1][j]和f[i][j-1]转移
要滚动
#include<stdio.h> #include<algorithm> #define cint const int & using namespace std; double v[2][5005]; int r,b; inline double V(cint a,cint b) { if (b<0) return 0; return v[a][b]; } int main() { scanf("%d%d",&r,&b); for (int i=0;i<=r;i++) for (int j=0;j<=b;j++) if (i+j) v[i&1][j]=max((double)i/(i+j)*(V(i&1^1,j)+1)+(double)j/(i+j)*(V(i&1,j-1)-1),0.0); printf("%.6lf",v[r&1][b]-0.0000005); }
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