ZOJ-3162-To Go or Not to Go

<span style="font-size:18px;"># include <cstdio>
# include <cstring>
# include <iostream>
using namespace std;

double dp[30][2];

void init()
{
memset(dp,0,sizeof(dp));
for(int i = 1;i < 30;i++){
dp[i][1] = dp[i-1][1] + dp[i-1][0] + (1<<i-1);
dp[i][0] = dp[i-1][1] + dp[i-1][0];
}
}

double fun(int n)
{
int cnt = 0;double sum = 0;
for(int i = 29;i >= 0;i--){
if(n &(1<<i)){
sum += dp[i+1][0];
sum += (double)(1<<i) * cnt;
cnt++;
}
}
return sum + cnt;
}

double calc(int a,int b){

int bit1,bit2;
double cnt=b-a+1,sum=0;

for(int i=29;i>=0;i--){
if(a&(1<<i)){
bit1=i;
break;
}
}
for(int i=29;i>=0;i--){
if(b&(1<<i)){
bit2=i;
break;
}
}

if(bit2-bit1==0){
double num=fun(b)-fun(a-1);
sum = num/(bit1+1);
}
else{
int x = (1<<(bit1+1)) - 1;
double num=fun(x) - fun(a-1);
sum = num/(bit1+1);

x = (1<<bit2);
num = fun(b)-fun(x) + 1;
sum += num/(bit2+1);
}
for(int i=bit1+2;i<=bit2;i++)    sum+=dp[i][1]/i;
return sum/cnt;
}

int main(){
int t;
init();
scanf("%d",&t);
while(t--){
int a,b;
scanf("%d%d",&a,&b);
printf("%.6lf\n",calc(a,b));
}
return 0;
}</span>