| # | Time | Username | Problem | Language | Result | Execution time | Memory |
|---|---|---|---|---|---|---|---|
| 518687 | fleimgruber | Keys (IOI21_keys) | C++17 | 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 "algolib/union-find.h"
#include <bits/stdc++.h>
using namespace std;
const int MAX_N = 300005;
int n;
vector<int> ans;
struct Edge {
int to, key; // key required
bool operator<(const Edge& o) const {
// cannot just use key, otherwise edges get lost (set)
return tie(key, to) < tie(o.key, o.to);
}
};
vector<int> out_can[MAX_N]; // only the to
set<Edge> out_blocked[MAX_N];
set<int> keys[MAX_N];
int par[MAX_N]; // parent in tree
UnionFind weakly(MAX_N); // weakly connected components
UnionFind<int> compressed(MAX_N);
// merge i into j, smaller to larger style
void merge(int i, int j) {
if (compressed.size(i) > compressed.size(j)) {
out_can[i].swap(out_can[j]);
out_blocked[i].swap(out_blocked[j]);
keys[i].swap(keys[j]);
}
compressed.connect(i, j); // tag of j is maintained
out_can[j].insert(out_can[j].end(),
out_can[i].begin(), out_can[i].end());
out_can[i].clear();
for (int key : keys[i])
if (keys[j].insert(key).second) { // promote
auto it = out_blocked[j].lower_bound({ -1, key });
while (it != out_blocked[j].end() && it->key == key) {
out_can[j].push_back(it->to);
it = out_blocked[j].erase(it);
}
}
keys[i].clear();
for (auto& x : out_blocked[i])
if (keys[j].find(x.key) == keys[j].end())
out_blocked[j].insert(x);
else if (!compressed.connected(j, x.to)) // pruning back edges
out_can[j].push_back(x.to);
out_blocked[i].clear();
return;
}
void solve() {
using pq_key = pair<int, int>; // size, vertex (roots order by size)
priority_queue<pq_key, vector<pq_key>, greater<pq_key>> roots;
// tags are the representatives (where keys & edges are stored)
for (int i = 0; i < n; i++) {
compressed.set_tag(i, i);
roots.push({ 1, i });
}
// != -1 means we already found an answer of size done_size
// so stop pushing to pq, but collect remaining components
int done_size = -1;
ans.assign(n, 0);
while (!roots.empty()) {
auto [_, r] = roots.top();
roots.pop();
// find any outgoing edge
bool has_outgoing = false;
while (!out_can[r].empty()) {
int to = out_can[r].back();
out_can[r].pop_back();
if (compressed.connected(r, to))
continue;
has_outgoing = true;
if (done_size != -1) // we're larger than the answer
break;
if (weakly.connected(r, to)) {
// merge with self. walk up parents
int j = compressed.tag(to);
do {
int jp = compressed.tag(par[j]);
merge(j, jp);
j = jp;
} while (j != r);
// we're still a root, but of larger size
roots.push({ compressed.size(r), r });
} else { // merge with other component
par[r] = to;
weakly.connect(r, to);
// we're no root any longer (no pq push)
}
break;
}
if (!has_outgoing) {
int size = compressed.size(r);
if (done_size != -1 && size != done_size)
break;
done_size = size;
ans[r] = 1;
}
}
for (int i = 0; i < n; i++) // everthing in their components too
if (ans[compressed.tag(i)])
ans[i] = 1;
}
vector<int> find_reachable(vector<int> r, vector<int> u,
vector<int> v, vector<int> c) {
n = r.size();
for (int i = 0; i < n; i++)
keys[i].insert(r[i]);
for (size_t i = 0; i < u.size(); i++)
for (int x = 0; x < 2; x++) {
if (r[u[i]] == c[i])
out_can[u[i]].push_back(v[i]);
else
out_blocked[u[i]].insert({ v[i], c[i] });
swap(u[i], v[i]);
}
solve();
return ans;
}