Submission #19372711

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;
const long long int MOD = 1e9 + 7;

int main(){
    int n, k;
    cin >> n >> k;

    map<int,int> table;
    for(int i=0; i<n; i++){
        int a;
        cin >> a;

        if(table.find(a) == table.end()) table[a] = 0;
        table[a] += 1;
    }

    vector<long long int> pow2(n+1);
    pow2[0] = 1;
    for(int i=0; i<n; i++){
        pow2[i+1] = pow2[i] * 2;
        pow2[i+1] %= MOD;
    }

    int m = table.size();// < 500 since (1+500) * 500 / 2 > 1e5
    vector<vector<long long int>> dp(m+1,vector<long long int>(1<<17));
    dp[0][0] = 1;
    int i = 0;
    for(auto t : table){
        int x = t.first;
        int num = t.second;

        for(int j=0; j<(1<<17); j++){
            dp[i+1][j] += dp[i][j] * pow2[num-1];// nC0 + nC2 + ... = [(1+1)^n + (1+(-1))^n] / 2 = 2^{n-1}
            dp[i+1][j] %= MOD;

            assert((j^x) < (1<<17));
            dp[i+1][j^x] += dp[i][j] * pow2[num-1];// nC1 + nC3 + ... = [(1+1)^n - (1+(-1))^n] / 2 = 2^{n-1}
            dp[i+1][j^x] %= MOD;
        }
        i += 1;
    }
    cout << dp[m][k] << endl;
    return 0;
}

Submission Info

Judge Result