Submission #1219628

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Source Code Expand

#include<bits/stdc++.h>
#define range(i,a,b) for(int i = (a); i < (b); i++)
#define rep(i,b) for(int i = 0; i < (b); i++)
#define all(a) (a).begin(), (a).end()
#define show(x)  cerr << #x << " = " << (x) << endl;
#define debug(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ")" << " " << __FILE__ << endl;
const int INF = 2000000000;
using namespace std;

//i番目のビットを返す
bool getBit(int num, int i){
    return ((num & (1 << i)) != 0);
}

//i番目を1にする
int setBit(int num, int i){
    return num | (1 << i);
}

//i番目を0にする
int clearBit(int num, int i){
    int mask = ~(1 << i);
    return num & mask;
}

//i番目をvで置き換える
int updateBit(int num, int i, int v){
    int mask = ~(1 << i);
    return (num & mask) | (v << i);
}

int main(){
    long long n, x;
    cin >> n >> x;

    long long w[33];
    rep(i,n) cin >> w[i];

    long long m = n / 2;
    n-=m;

    vector<long long> a, b;
    rep(i,(1 << n)){
        long long sum = 0;
        rep(j,n){
            if(getBit(i,j)) sum += w[j];
        }
        a.emplace_back(sum);
    }
    rep(i,(1 << m)){
        long long sum = 0;
        rep(j,m){
            if(getBit(i,j)) sum += w[n + j];
        }
        b.emplace_back(sum);
    }

    sort(all(b));
    long long cnt = 0;
    rep(i,a.size()){
        cnt += upper_bound(all(b), x - a[i]) - lower_bound(all(b), x - a[i]);
    }
    cout << cnt << endl;
}

Submission Info

Judge Result