HDU 5694 BD String

递归地计算就可以。

#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
using namespace std;

long long len[70];
long long L,R;

void init()
{
    len[1]=1;
    for(int i=2; i<=60; i++) len[i]=2*len[i-1]+1;
}

long long f(long long p)
{
    if(p<=0) return 0;
    if(p==1) return 1;
    int l=1,r=60;
    int ans;
    while(l<=r)
    {
        int mid=(l+r)/2;
        if(len[mid]<=p) ans=mid,l=mid+1;
        else r=mid-1;
    }
    long long res=0;
    res=res+(len[ans]+1)/2;
    long long g=p-(len[ans]+2)+1;
    if(len[ans]+1<=p) res++;
    if(len[ans]+2<=p)
    {
        long long pp=len[ans]-g;
        long long a=len[ans]-(len[ans]+1)/2;
        long long b=pp-f(pp);
        res=res+a-b;
    }
    return res;
}

int main()
{
    init();
    int T; scanf("%d",&T);
    while(T--)
    {
        scanf("%lld%lld",&L,&R);
        printf("%lld
",f(R)-f(L-1));
    }
    return 0;
}