#include "simurgh.h"
#include <bits/stdc++.h>
using namespace std;
#define ll int
#define endl "\n"
#define sz(x) (ll)x.size()
#define F first
#define S second
#define pb push_back
#define ins insert
typedef vector <ll> vi;
typedef pair <ll,ll> ii;
typedef vector <ii> vii;
#define dbg(x) cout<<#x<<": "<<x<<endl;
#define dbg2(x,y) cout<<#x<<": "<<x<<" "<<#y<<": "<<y<<endl;
#define dbg3(x,y,z) cout<<#x<<": "<<x<<" "<<#y<<": "<<y<<" "<<#z<<": "<<z<<endl;
void printVct(vi &v){
for (ll i =0; i<sz(v); i++){
cout<<v[i]<<" ";
}
cout<<endl;
}
vector < vii > adj;
vi dp, h, vis;
vi bridges;
void dfs(ll u, ll height, ll p){
// dbg(u);
h[u] = height;
dp[u] = height;
vis[u] = 1;
for (ll i =0; i<sz(adj[u]); i++){
ll c = adj[u][i].F;
if (c == p) continue;
if (!vis[c]){
dfs(c, height+1, u);
}
dp[u] = min(dp[u], dp[c]);
if (dp[u] == dp[c]){
// dbg2(u,c);
bridges[adj[u][i].S] = 0;
}
}
}
vi par, siz;
ll fnd(ll x){
if (x == par[x]) return x;
return par[x] = fnd(par[x]);
}
void onion(ll a, ll b){
a = fnd(a);
b = fnd(b);
if (a != b){
if (siz[a] < siz[b]) swap(a,b);
par[b] = a;
siz[a] += siz[b];
}
}
//create span tree: O(N + M)
vi span_tree(ll n, ll m, ll processed_node, vi &u, vi &v, vi &royal_edges, vi &royal_edges_grid, ll on_edge = -1){
vi q;
//init DSU:
par.resize(n);
for (ll j =0; j<n; j++){
par[j] = j;
}
siz.assign(n, 1);
//connect on edge:
if (on_edge != -1){
onion(u[on_edge], v[on_edge]);
q.pb(on_edge);
}
//connect royal edges:
for (ll j =0; j<sz(royal_edges); j++){
ll a = v[royal_edges[j]], b = u[royal_edges[j]];
onion(a, b);
q.pb(royal_edges[j]);
}
//rest of the edges without adding illegal edges
for (ll j=0; j<m && sz(q) < n-1; j++){
if (royal_edges_grid[j]) continue;
ll a = v[j], b = u[j];
if (a != processed_node && b != processed_node && fnd(a) != fnd(b)){
onion(a,b);
q.pb(j);
}
}
// cout<<"q:";
// printVct(q);
//validate span tree:
bool ok = true;
for (ll j =1; j<n; j++){
if (fnd(j) != fnd(j-1)){
ok = false;
}
}
if (!ok){
q = vi();
}
return q;
}
vi find_roads(int n, vi u, vi v) {
ll m = sz(u);
adj.assign(n, vii());
for (ll i =0; i<m; i++){
adj[u[i]].pb(ii(v[i], i));
adj[v[i]].pb(ii(u[i], i));
}
// step 1: find all bridges and mark them as royal
bridges.assign(m, 1);
h.resize(n);
vis.assign(n, 0);
dp.resize(n);
dfs(0,0,-1);
vi royal_edges, processed_edgs(m, 0), royal_edges_grid(m, 0);
for (ll i =0; i<m; i++){
if (bridges[i]){
processed_edgs[i] = 1;
royal_edges.pb(i);
royal_edges_grid[i] = 1;
}
}
// cout<<"royal:";
// printVct(royal_edges);
//step 2:
for (ll i =0; i<n; i++){ //process nodes one by one
// dbg(i);
vi edges_to_process, q;
for (ll j =0; j<sz(adj[i]); j++){
ll id = adj[i][j].S;
if (!processed_edgs[id]){
edges_to_process.pb(id);
processed_edgs[id] = 1;
}
}
if (sz(edges_to_process) == 0) continue;
// cout<<"edges_to_process: ";
// printVct(edges_to_process);
// return vi();
//create span tree: O(N + M)
q = span_tree(n,m,i,u,v,royal_edges,royal_edges_grid);
// printVct(q);
bool empty_is_valid = !q.empty();
//Turn processed edges on/off
if (sz(edges_to_process) == 1){
ll val = count_common_roads(q);
q = span_tree(n,m,i,u,v,royal_edges,royal_edges_grid,edges_to_process[0]);
if (q.empty()) continue;
ll x = count_common_roads(q);
if (x > val){
royal_edges.pb(edges_to_process[0]);
royal_edges_grid[edges_to_process[0]] = 1;
}
}
else{
vii res; //res, id
for (ll j = 0; j<sz(edges_to_process); j++){
q = span_tree(n,m,i,u,v,royal_edges,royal_edges_grid,edges_to_process[j]);
if (q.empty()) continue;
// printVct(q);
ll x = count_common_roads(q);
res.pb(ii(x,edges_to_process[j]));
}
ll mini = res[0].F, maxi = res[0].S;
for (ll j =0; j<sz(res); j++){
mini = min(res[j].F, mini);
maxi = max(res[j].F, maxi);
}
if (mini == maxi){
for (ll j =0; j<sz(res); j++){
royal_edges.pb(res[j].S);
royal_edges_grid[res[j].S] = 1;
}
}
else{
for (ll j =0; j<sz(res); j++){
if (res[j].F == maxi){
royal_edges.pb(res[j].S);
royal_edges_grid[res[j].S] = 1;
}
}
}
}
}
// cout<<endl<<"ans:";
// printVct(royal_edges);
return royal_edges;
}
/*
5 7
0 1
0 2
0 3
1 2
1 3
2 3
3 4
0 1 5 6
5 5
0 1
1 2
1 3
2 3
3 4
0 1 2 4
4 6
0 1
0 2
0 3
1 2
1 3
2 3
0 1 5
*/
Compilation message
simurgh.cpp: In function 'vi find_roads(int, vi, vi)':
simurgh.cpp:160:8: warning: unused variable 'empty_is_valid' [-Wunused-variable]
160 | bool empty_is_valid = !q.empty();
| ^~~~~~~~~~~~~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
1 ms |
344 KB |
WA in grader: NO |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
1 ms |
344 KB |
WA in grader: NO |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
1 ms |
344 KB |
WA in grader: NO |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
0 ms |
348 KB |
correct |
| 2 |
Runtime error |
0 ms |
348 KB |
Execution killed with signal 11 |
| 3 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
1 ms |
344 KB |
WA in grader: NO |
| 2 |
Halted |
0 ms |
0 KB |
- |
