2020 CCPC Wannafly Winter Camp Day2 B 萨博的方程式

#include<iostream>
#include<cstring>
#include<algorithm>
#include<cmath>
#include<cstdlib>
#include<climits>
#include<stack>
#include<vector>
#include<queue>
#include<set>
#include<bitset>
#include<map>
//#include<regex>
#include<cstdio>
#pragma GCC optimize(2)
#define up(i,a,b)  for(int i=a;i<b;i++)
#define dw(i,a,b)  for(int i=a;i>b;i--)
#define upd(i,a,b) for(int i=a;i<=b;i++)
#define dwd(i,a,b) for(int i=a;i>=b;i--)
//#define local
typedef long long ll;
typedef unsigned long long ull;
const double esp = 1e-6;
const double pi = acos(-1.0);
const int INF = 0x3f3f3f3f;
const int inf = 1e9;
using namespace std;
ll read()
{
	char ch = getchar(); ll x = 0, f = 1;
	while (ch<'0' || ch>'9') { if (ch == '-')f = -1; ch = getchar(); }
	while (ch >= '0' && ch <= '9') { x = x * 10 + ch - '0'; ch = getchar(); }
	return x * f;
}
typedef pair<int, int> pir;
#define lson l,mid,root<<1
#define rson mid+1,r,root<<1|1
#define lrt root<<1
#define rrt root<<1|1
const int N = 55;
const int mod = 1e9 + 7;
ll quickpow(ll k,ll m)
{
	ll res = 1;
	while (m)
	{
		if (m & 1)res = res * k%mod;
		k = k * k%mod;
		m >>= 1;
	}
	return res;
}
ll dp[N][2][2];
ll a[N];
ll n, k;
ll cal(int pos)
{
	if (pos < 0)return 1;
	memset(dp, 0, sizeof(dp));
	dp[0][0][1] = 1;
	int cur = 0;
	upd(i, 1, n)
	{
		if (a[i] >> pos & 1)
		{
			cur++;
			dp[cur][0][0] = (dp[cur][0][0] + dp[cur - 1][1][0] * (a[i] - (1ll << pos) + 1ll) % mod + (1ll << pos)*(dp[cur - 1][0][1] + dp[cur - 1][0][0]) % mod) % mod;
			dp[cur][0][1] = (dp[cur][0][1] + dp[cur - 1][1][1] * (a[i] - (1ll << pos) + 1ll) % mod) % mod;
			dp[cur][1][0] = (dp[cur][1][0] + dp[cur - 1][0][0] * (a[i] - (1ll << pos) + 1ll) % mod + (1ll << pos)*(dp[cur - 1][1][0] + dp[cur - 1][1][1]) % mod) % mod;
			dp[cur][1][1] = (dp[cur][1][1] + dp[cur - 1][0][1] * (a[i] - (1ll << pos) + 1ll) % mod) % mod;
		}
		else
		{
			dp[cur][0][0] = (dp[cur][0][0] * (a[i]+1)) % mod;
			dp[cur][0][1] = (dp[cur][0][1] * (a[i]+1)) % mod;
			dp[cur][1][0] = (dp[cur][1][0] * (a[i]+1)) % mod;
			dp[cur][1][1] = (dp[cur][1][1] * (a[i]+1)) % mod;
		}
	}
	ll inv = quickpow((1 << pos), mod - 2);
	ll res = dp[cur][k >> pos & 1][0]*inv%mod;
	if ((cur & 1) == (k >> pos & 1))
	{
		upd(i, 1, n)
			if (a[i] >> pos & 1)a[i] ^= (1ll << pos);
		return (res + cal(pos - 1))%mod;
	}
	else return res%mod;
}
int main()
{
	while (~scanf("%lld %lld", &n, &k))
	{
		memset(dp, 0, sizeof(dp));
		upd(i, 1, n)
		{
			a[i] = read();
		}
		cout << cal(30)%mod << endl;
	}
	return 0;
}