简单DP。。注意到一个人的血量为0,他就挂了,不能再推到其他情况了。。。输入的是反的。。。
#include <iostream> #include <queue> #include <stack> #include <map> #include <set> #include <bitset> #include <cstdio> #include <algorithm> #include <cstring> #include <climits> #include <cstdlib> #include <cmath> #include <time.h> #define maxn 2005 #define maxm 150000 #define eps 1e-10 #define mod 1000000007 #define INF 999999999 #define lowbit(x) (x&(-x)) #define mp mark_pair #define ls o<<1 #define rs o<<1 | 1 #define lson o<<1,L,mid #define rson o<<1 | 1,mid+1,R //typedef vector<int>::iterator IT; typedef long long LL; //typedef int LL; using namespace std; LL qpow(LL a,LL b){LL res=1,base=a;while(b){if(b%2)res=res*base;base=base*base;b/=2;}return res;} LL powmod(LL a,base=a;while(b){if(b%2)res=res*base%mod;base=base*base%mod;b/=2;}return res;} void scanf(int &__x){__x=0;char __ch=getchar();while(__ch==' '||__ch=='\n')__ch=getchar();while(__ch>='0'&&__ch<='9')__x=__x*10+__ch-'0',__ch = getchar();} LL gcd(LL _a,LL _b){if(!_b) return _a;else return gcd(_b,_a%_b);} // head double dp[maxn][maxn]; double t1[maxn],t2[maxn]; double a,b,c; int n,m; void read(void) { for(int i = 1; i <= 6; i++) scanf("%lf",&t1[i]); for(int i = 1; i <= 6; i++) scanf("%lf",&t2[i]); } void work(void) { a = b = c = 0; for(int i = 1; i <= 6; i++) for(int j = 1; j <= 6; j++) { if(i == j) c += t1[i] * t2[j]; if(i < j) a += t1[i] * t2[j]; if(i > j) b += t1[i] * t2[j]; } for(int i = 0; i <= n+1; i++) for(int j = 0; j <= m+1; j++) dp[i][j] = 0; dp[n][m] = 1; if(fabs(1 - c) < eps) { printf("0.000000\n"); return; } double t = 1 - c; for(int i = n; i >= 0; i--) for(int j = m; j >= 0; j--) { if(i == n && j == m) continue; if(i && j ) dp[i][j] = (a * dp[i+1][j] + b * dp[i][j+1]) / t; else if(i) dp[i][j] = (b * dp[i][j+1]) / t; else if(j) dp[i][j] = (a * dp[i+1][j]) / t; else dp[i][j] = 0; } double ans = 0; for(int i = 1; i <= n; i++) ans += dp[i][0]; printf("%.6f\n",ans); } int main(void) { while(scanf("%d%d",&m,&n)!=EOF) { read(); work(); } return 0; }