# | Time | Username | Problem | Language | Result | Execution time | Memory |
---|---|---|---|---|---|---|---|
540709 | Berted | Port Facility (JOI17_port_facility) | C++14 | 0 ms | 0 KiB |
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 <iostream>
#include <set>
#include <vector>
#include <algorithm>
using namespace std;
const int MD = 1e9 + 7;
int T, N, cnt, A[2000001], par[1000001], pos[1000001];
vector<int> mem[1000001];
int color[1000001] = {}, mx[1000001][2][2];
set<int> S;
int find(int x) {return (x == par[x]) ? x : find(par[x]);}
inline bool join(int a, int b) {
int ka = color[a], kb = color[b];
//cerr << "JOIN: " << a << " " << b << " called\n";
a = find(a), b = find(b);
if (a == b) return ka != kb;
else {
cnt--;
if (mem[a].size() < mem[b].size()) swap(a, b);
par[b] = a;
while (mem[b].size()) {
mem[a].push_back(mem[b].back());
color[mem[b].back()] ^= (ka == kb);
mem[b].pop_back();
}
for (int i = 0; i < 2; i++) {
vector<int> temp = {mx[a][i][0], mx[a][i][1], mx[b][i ^ (ka == kb)][0], mx[b][i ^ (ka == kb)][1]};
sort(temp.begin(), temp.end());
mx[a][i][0] = temp[3];
mx[a][i][1] = temp[2];
}
//cerr << b << " now rooted to " << a << "\n";
return 1;
}
}
int main() {
ios :: sync_with_stdio(0); cin.tie(0);
bool yes = true;
cin >> N;
cnt = N;
S.clear();
for (int i = 0; i < N; i++) {
pos[i] = -1;
par[i] = i;
color[i] = 0;
for (int j = 0; j < 2; j++)
for (int k = 0; k < 2; k++) mx[i][j][k] = -1;
mem[i] = {i};
}
for (int i = 0; i < N; i++) {
int a, b; cin >> a >> b;
A[a - 1] = i; A[b - 1] = i;
//cerr << i << ": " << a << " " << b << "\n";
}
for (int i = 0; i < 2 * N && yes; i++) {
int u; u = A[i];
if (pos[u] == -1) {
//cerr << "IS: " << i << "\n";
S.insert(i);
pos[u] = i;
} else if (pos[u] != -2) {
auto it = S.upper_bound(pos[u]);
while (it != S.end()) {
int v = *it, vv = A[v];
yes &= join(vv, u);
//cerr << "Check: " << vv << " " << v << " " << find(vv) << " " << color[vv] << "\n";
if (false) it = S.erase(it);
else {it++;}
}
S.erase(pos[u]);
pos[u] = -2;
}
mx[find(u)][color[u]][1] = mx[find(u)][color[u]][0];
mx[find(u)][color[u]][0] = i;
}
if (yes) {
int res = 1;
for (int i = 0; i < cnt; i++) {
res = res << 1;
if (res >= MD) res -= MD;
}
cout << res << "\n";
} else {cout << "0\n";}
return 0;
}