This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include <bits/stdc++.h>
#define pb push_back
#define all(v) ((v).begin(), (v).end())
#define sortv(v) sort(all(v))
#define sz(v) ((int)(v).size())
#define uniqv(v) (v).erase(unique(all(v)), (v).end())
#define umax(a, b) (a)=max((a), (b))
#define umin(a, b) (a)=min((a), (b))
#define FOR(i,a,b) for(int i = (a); i <= (b); i++)
#define rep(i,n) FOR(i,1,n)
#define rep0(i,n) FOR(i,0,(int)(n)-1)
#define FI first
#define SE second
#define INF 2000000000
#define INFLL 1000000000000000000LL
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const ll DIV = 1000000007;
const int MAX_N = 1000000;
int N;
vector<pii> vt;
bool zero = false;
vector<int> gp[MAX_N*2+1];
int c[MAX_N*2+1];
/*struct SEG{
struct NODE{
int l=-1, r=-1;
vector<int> v;
int sz=0;
};
vector<NODE> seg;
int SZ, cnt;
void Init(int x){
SZ = x; seg.resize(SZ*2);
cnt = 1;
init(0, 1, SZ);
}
void init(int idx, int s, int e){
seg[idx].v.reserve(e-s+1);
if(s==e) return;
seg[idx].l = cnt++; seg[idx].r = cnt++;
init(seg[idx].l, s, (s+e)/2);
init(seg[idx].r, (s+e)/2+1, e);
}
void Update(int x){
update(0, 1, SZ, x);
}
void update(int idx, int s, int e, int k){
//cout<<idx<<" "<<s<<" "<<e<<" "<<x<<" "<<y<<endl;
seg[idx].v.pb(k);
if(s==e) return;
if(k<=(s+e)/2){
update(seg[idx].l, s, (s+e)/2, k);
}else{
update(seg[idx].r, (s+e)/2+1, e, k);
}
}
void Calc(int x, int y){
calc(0, 1, SZ, x, y);
}
void calc(int idx, int s, int e, int x, int y){
if(seg[idx].v.empty()) return;
//cout<<idx<<" "<<s<<" "<<e<<" "<<x<<" "<<y<<endl;
if(x<=s && e<=y){
int k=0;
//cout<<idx<<" "<<s<<" "<<e<<" "<<x<<" "<<y<<endl;
while(!seg[idx].v.empty()){
int t = seg[idx].v.back(); seg[idx].v.pop_back();
k = max(k, t);
gp[t].pb(y); gp[y].pb(t);
}
if(k!=0) seg[idx].v.pb(k);
return;
}else if(x>e || y<s) return;
calc(seg[idx].l, s, (s+e)/2, x, y);
calc(seg[idx].r, (s+e)/2+1, e, x, y);
}
};
SEG Seg;*/
vector<int> vv;
void bfs(int x){
vv.pb(x);
while(!vv.empty()){
x = vv.back(); vv.pop_back();
//cout<<x<<endl;
for(int i : gp[x]){
if(c[i]==0){
c[i] = 3 - c[x];
vv.pb(i);
}else if(c[i]==c[x]){
zero=true;
return;
}
}
}
}
set<int> st;
void Calc(int x, int y){
set<int>::iterator it = st.lower_bound(x);
while(it!=st.end() && (*it)<y){
//cout<<(*it)<<endl;
gp[(*it)].pb(y); gp[y].pb((*it));
it++;
}
}
void Update(int x){
st.insert(x);
}
vector<int> sc;
int main(){
scanf("%d", &N);
for(int i=1; i<=N; i++){
int a, b;
scanf("%d%d", &a, &b);
vt.pb({a, b});
}
sort(vt.begin(), vt.end());
int idx = 0;
//UF.init(N*2);
//Seg.Init(N*2);
for(int i=1; i<=N*2; i++){
if(idx<N && vt[idx].first==i){
//cout<<vt[idx].first<<" "<<vt[idx].second<<endl;
Calc(vt[idx].first, vt[idx].second);
Update(vt[idx].second);
idx++;
}else{
sc.pb(i);
}
}
ll ans = 1;
for(int i : sc){
//cout<<i<<endl;
if(c[i]==0){
c[i] = 1;
bfs(i);
if(zero){
printf("0");
return 0;
}
ans = (ans*(ll)2)%DIV;
}
}
cout<<ans;
return 0;
}
Compilation message (stderr)
port_facility.cpp: In function 'int main()':
port_facility.cpp:129:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
scanf("%d", &N);
~~~~~^~~~~~~~~~
port_facility.cpp:132:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
scanf("%d%d", &a, &b);
~~~~~^~~~~~~~~~~~~~~~
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