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 = 0)
{
    if(R<Lt || L>Rt) return 0;
    if(Lt < L && R < Rt) return 1;
    double H = (L+R)/2;
    if(k == K) return (Lt<H && H<Rt)?1.:0.;
    double p = T<H?1-P:P;
    return dfs(L,H,k+1)*p + dfs(H,R,k+1)*(1.-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
",dfs(L,R));
    return 0;
}