Aizu 2301 Sleeping Time（概率，剪枝）

根据概率公式dfs即可，判断和区间[T-E,T+E]是否有交，控制层数。

#include<bits/stdc++.h>

using namespace std;

int K,R,L;

double P,E,T;

double Lt,Rt;

double dfs(double L,double R,int k = )

{

    if(R<Lt || L>Rt) return ;

    if(Lt < L && R < Rt) return ;

    double H = (L+R)/;

    if(k == K) return (Lt<H && H<Rt)?.:.;

    double p = T<H?-P:P;

    return dfs(L,H,k+)*p + dfs(H,R,k+)*(.-p);

}

//#define LOCAL

int main()

{

#ifdef LOCAL

    freopen("in.txt","r",stdin);

#endif

    scanf("%d%d%d",&K,&L,&R);

    scanf("%lf%lf%lf",&P,&E,&T);

    Lt = T-E, Rt = T+E;

    printf("%lf\n",dfs(L,R));

    return ;

}