1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
#include <iostream>
#include <bitset>
#include <unordered_set>

constexpr int maxn = 2e5 + 7, maxm = 4e5 + 7, mod = 1e9 + 7;
int n, m;
std::unordered_set<std::bitset<maxn>> reachable;
std::bitset<maxn> bs;
std::pair<int, int> buttons[maxm];

void input() {
    scanf("%d%d", &n, &m);
    int x, y;
    for(int i = 0; i < n; i++) {
        scanf("%d", &x);
        bs[i] = x;
    }
    reachable.insert(bs);
    for(int i = 0; i < m; i++) {
        scanf("%d%d", &x, &y);
        buttons[i] = {x, y};
    }
}

void brut() {
    reachable.insert(bs);
    for(int i = 0; i < m; i++) {
        auto [x, y] = buttons[i];
        x--; y--;
        if(bs[x] != bs[y])
            continue;
        bs[x] = !bs[x];
        bs[y] = !bs[y];
        if(reachable.find(bs) == reachable.end())
            brut();
        bs[x] = !bs[x];
        bs[y] = !bs[y];
    }
}

void debug() {
    for(const auto& b : reachable) {
        for(int i = 0; i < n; i++)
            std::cerr << b[i];
        std::cerr << std::endl;
    }
}

int main() {
    input();
    brut();
    printf("%lld", reachable.size() % mod);
//    debug();
    return 0;
}