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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")
struct PairHash {
inline std::size_t operator()(const std::pair<int, int> &v) const { return v.first * 31 + v.second; }
};
#define MAX_N 202020
#define INF 987654321
#define EPS 1e-9
#define ll long long
#define pll pair<ll, ll>
#define vpll vector<pll>
#define vall3 vector<array<ll,3>>
#define all3 array<ll,3>
#define all5 array<ll,5>
#define vall5 vector<all5>
#define vll vector<ll>
#define vi vector<int>
#define vs vector<string>
#define usll unordered_set<ll>
#define uspll unordered_set<pll, PairHash>
#define umll unordered_map<ll,ll>
#define vvs vector<vs>
#define vvll vector<vll>
#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); }
using namespace std;
ll uf[MAX_N];
ll find(ll u) {
return uf[u] == u ? u : uf[u] = find(uf[u]);
}
void uni(ll u, ll v) {
ll pu = find(u), pv = find(v);
uf[pu] = uf[pv] = min(pu, pv);
}
string solve(ll n, vpll& A) {
for(ll i = 0; i <= n; i++) uf[i] = i;
for(auto& [l, r] : A)
uni(l - 1, r);
return find(0) == find(n) ? "Yes" : "No";
}
int main() {
ios_base::sync_with_stdio(0);
ios::sync_with_stdio(0);
cin.tie(0);
ll tc = 1;
for (ll i = 1; i <= tc; i++) {
ll n, q;
cin>>n>>q;
vpll A(q);
for(ll j = 0; j < q; j++) cin>>A[j].first>>A[j].second;
cout<<solve(n, A)<<endl;
}
return 0;
}
|
