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| #include <bits/stdc++.h>
#pragma optimization_level 3
#pragma GCC optimize("Ofast,no-stack-protector,unroll-loops,fast-math,O3")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx")
#pragma GCC optimize("Ofast")
#pragma GCC target("avx,avx2,fma")
#pragma GCC optimization ("unroll-loops")
using namespace std;
struct PairHash {
inline std::size_t operator()(const std::pair<int, int> &v) const { return v.first * 31 + v.second; }
};
#define Code ios_base::sync_with_stdio(false);
#define By ios::sync_with_stdio(0);
#define Sumfi cout.tie(NULL);
using ll = long long;
using ld = long double;
const ld PI = 3.14159265358979323846;
const ll INF = 1e18;
const ld EPS = 1e-9;
const ll MAX_N = 202020;
const ll mod = 998244353;
typedef pair<ll, ll> pll;
typedef vector<pll> vpll;
typedef array<ll,3> all3;
typedef array<ll,5> all5;
typedef vector<all3> vall3;
typedef vector<all5> vall5;
typedef vector<ll> vll;
typedef vector<vll> vvll;
typedef vector<int> vi;
typedef vector<string> vs;
typedef vector<vs> vvs;
typedef unordered_set<ll> usll;
typedef unordered_set<pll, PairHash> uspll;
typedef unordered_map<ll, ll> umll;
#define rep(i,n) for(ll i=0;i<n;i++)
#define rrep(i,m,n) for(ll i=n;i>=m;i--)
#define all(a) begin(a), end(a)
#define rall(a) rbegin(a), rend(a)
ll __gcd(ll x, ll y) { return !y ? x : __gcd(y, x % y); }
ll __lcm(ll x, ll y) { return x * y / __gcd(x,y); }
using namespace std;
ll vis[MAX_N];
void dfs(ll u, vvll& adj, ll& c, ll& e) {
vis[u] = true;
c += 1;
e += adj[u].size();
for(auto& v : adj[u])
if(!vis[v])
dfs(v, adj, c, e);
}
ll solve(ll n, vpll& A) {
vvll adj(n);
for(auto& [u, v] : A) {
adj[u-1].push_back(v-1);
adj[v-1].push_back(u-1);
}
ll res = 1;
rep(i,n) {
if(!vis[i]) {
ll v = 0, e = 0;
dfs(i, adj, v, e);
if(v * 2 == e) res = (res * 2) % mod;
else return 0;
}
}
return res;
}
int main() {
Code By Sumfi
ll tc = 1;
for (ll i = 1; i <= tc; i++) {
ll n, m;
cin>>n>>m;
vpll A(m);
rep(i, m) cin>>A[i].first>>A[i].second;
cout<<solve(n, A)<<endl;
}
return 0;
}
|
