Codeforces 1151C Problem for Nazar

大意: 给定一个无限长的序列, 求区间和.

这题比赛的时候改半天没改出来, 以后做这种模拟应该把思路理清再写.

就是利用分块的思想, 预处理出每一块的和, 再询问时用中间整块的和加上左右部分块的和.

#include <iostream>
#include <algorithm>
#include <cstdio>
#include <math.h>
#include <set>
#include <map>
#include <queue>
#include <string>
#include <string.h>
#include <bitset>
#define REP(i,a,n) for(int i=a;i<=n;++i)
#define PER(i,a,n) for(int i=n;i>=a;--i)
#define hr putchar(10)
#define pb push_back
#define lc (o<<1)
#define rc (lc|1)
#define mid ((l+r)>>1)
#define ls lc,l,mid
#define rs rc,mid+1,r
#define x first
#define y second
#define io std::ios::sync_with_stdio(false)
#define endl '
'
#define DB(a) ({REP(__i,1,n) cout<<a[__i]<<' ';hr;})
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
const int P = 1e9+7, INF = 0x3f3f3f3f;
ll gcd(ll a,ll b) {return b?gcd(b,a%b):a;}
ll qpow(ll a,ll n) {ll r=1%P;for (a%=P;n;a=a*a%P,n>>=1)if(n&1)r=r*a%P;return r;}
ll inv(ll x){return x<=1?1:inv(P%x)*(P-P/x)%P;}
inline int rd() {int x=0;char p=getchar();while(p<'0'||p>'9')p=getchar();while(p>='0'&&p<='9')x=x*10+p-'0',p=getchar();return x;}
//head



#ifdef ONLINE_JUDGE
const int N = 1e6+10;
#else
const int N = 111;
#endif

const int mx = 62;
int cnt;
ll a[N], st[N], sum[N], inv2 = (1+P)/2;

int blo(ll x) {
	return lower_bound(a+1,a+1+mx,x)-a;
}
ll L(ll x) {
	return a[blo(x)-1]+1;
}
ll R(ll x) {
	return a[blo(x)];
}
ll num(ll x) {
	ll n = x-L(x)+1;
	return (st[blo(x)]+(n-1)*2)%P;
}
void init() {
	REP(i,1,mx) a[i] = (1ll<<i)-1;
	st[1]=1,st[2]=2;
	REP(i,3,mx) st[i] = (st[i-2]+(1ll<<i-2))%P;
	sum[1]=1,sum[2]=7;
	REP(i,3,mx) {
		ll n = (1ll<<i-1)%P;
		sum[i] = (sum[i-1]+n*st[i]%P+n*(n-1)%P)%P;
	}
}

ll solve(ll l, ll r) {
	ll ans = 0;
	if (blo(l)==blo(r)) { 
		ans = (num(r)+num(l))%P*(r%P-l%P+1)%P*inv2%P;
	}
	else ans=(solve(l,R(l))+solve(L(r),r)+sum[blo(r)-1]-sum[blo(l)])%P;
	return ans;
}

int main() {
	init();
	ll l, r;
	cin>>l>>r;
	ll ans = solve(l,r);
	if (ans<0) ans+=P;
	cout<<ans<<endl;
}