Submission #969083

#	Time	Username	Problem	Language	Result	Execution time	Memory
969083		GrindMachine	Simurgh (IOI17_simurgh)	C++17	32 / 100	154 ms	6176 KiB

simurgh

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
 
using namespace std;
using namespace __gnu_pbds;
 
template<typename T> using Tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
typedef long long int ll;
typedef long double ld;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
 
#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL)
#define pb push_back
#define endl '\n'
#define sz(a) (int)a.size()
#define setbits(x) __builtin_popcountll(x)
#define ff first
#define ss second
#define conts continue
#define ceil2(x,y) ((x+y-1)/(y))
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define yes cout << "Yes" << endl
#define no cout << "No" << endl
 
#define rep(i,n) for(int i = 0; i < n; ++i)
#define rep1(i,n) for(int i = 1; i <= n; ++i)
#define rev(i,s,e) for(int i = s; i >= e; --i)
#define trav(i,a) for(auto &i : a)
 
template<typename T>
void amin(T &a, T b) {
    a = min(a,b);
}
 
template<typename T>
void amax(T &a, T b) {
    a = max(a,b);
}
 
#ifdef LOCAL
#include "debug.h"
#else
#define debug(x) 42
#endif
 
/*
 
refs:
https://codeforces.com/blog/entry/53595?#comment-376568
 
*/
 
const int MOD = 1e9 + 7;
const int N = 500 + 5;
const int inf1 = int(1e9) + 5;
const ll inf2 = ll(1e18) + 5;
 
#include "simurgh.h"

struct DSU {
    vector<int> par, rankk, siz;

    DSU() {

    }

    DSU(int n) {
        init(n);
    }

    void init(int n) {
        par = vector<int>(n + 1);
        rankk = vector<int>(n + 1);
        siz = vector<int>(n + 1);
        rep(i, n + 1) create(i);
    }

    void create(int u) {
        par[u] = u;
        rankk[u] = 0;
        siz[u] = 1;
    }

    int find(int u) {
        if (u == par[u]) return u;
        else return par[u] = find(par[u]);
    }

    bool same(int u, int v) {
        return find(u) == find(v);
    }

    void merge(int u, int v) {
        u = find(u), v = find(v);
        if (u == v) return;

        if (rankk[u] == rankk[v]) rankk[u]++;
        if (rankk[u] < rankk[v]) swap(u, v);

        par[v] = u;
        siz[u] += siz[v];
    }
};

int f(vector<int> v){
	return count_common_roads(v);
}

vector<pii> adj[N];
vector<int> ord;
vector<int> tin(N);
vector<pii> low(N);
vector<bool> vis(N);
int timer = 1;
vector<int> spanning;
vector<pii> par(N);

void dfs1(int u, int p){
	vis[u] = 1;
	tin[u] = timer++;
	low[u] = {tin[u],-1};

	for(auto [v,id] : adj[u]){
		if(v == p) conts;
		if(vis[v]){
			amin(low[u],{tin[v],id});
		}
		else{
			spanning.pb(id);
			par[v] = {u,id};
			dfs1(v,u);
			amin(low[u],low[v]);
		}
	}

	ord.pb(u);
}

std::vector<int> find_roads(int n, std::vector<int> U, std::vector<int> V) {
	int m = sz(U);
	rep(i,m){
		int u = U[i], v = V[i];
		adj[u].pb({v,i}), adj[v].pb({u,i});
	}

	dfs1(0,-1);

	vector<int> status(m,-1);
	int original = f(spanning);

	trav(u,ord){
		// find the val of the incoming span edge
		if(!u) conts;
		auto [p,pid] = par[u];
		if(low[u].ff > tin[p]){
			status[pid] = 1;
			conts;
		}

		int cyc_id = low[u].ss;
		int x = U[cyc_id], y = V[cyc_id];
		if(tin[x] < tin[y]) swap(x,y);
		vector<int> pending;

		while(x != y){
			auto [p,pid] = par[x];
			if(status[pid] != -1){
				auto curr = spanning;
				curr.erase(find(all(curr),pid));
				curr.pb(cyc_id);
				int val = f(curr);
				int cyc_status = val+status[pid]-original;
				
				while(!pending.empty()){
					int edge_id = pending.back();
					pending.pop_back();
					curr = spanning;
					curr.erase(find(all(curr),edge_id));
					curr.pb(cyc_id);
					val = f(curr);
					status[edge_id] = original+cyc_status-val;
				}

				break;
			}

			x = p;
			pending.pb(pid);
		}

		if(pending.empty()) conts;

		// full cycle, none known
		pending.pb(cyc_id);
		auto curr = spanning;
		curr.pb(cyc_id);
		map<int,vector<int>> mp;

		trav(id,pending){
			curr.erase(find(all(curr),id));
			int val_without = f(curr);
			curr.pb(id);
			mp[val_without].pb(id);
		}

		if(sz(mp) == 1){
			// all 0
			trav(id,pending){
				status[id] = 0;
			}
		}
		else{
			assert(sz(mp) == 2);
			trav(id,mp.begin()->second){
				status[id] = 1;
			}
			trav(id,(--mp.end())->second){
				status[id] = 0;
			}
		}
	}

	auto get = [&](vector<int> edges){
		// edges form a star at some node u
		DSU dsu(n);
		trav(id,edges){
			dsu.merge(U[id],V[id]);
		}

		auto curr = edges;
		int extra = 0;

		trav(id,spanning){
			int u = U[id], v = V[id];
			if(dsu.same(u,v)) conts;
			dsu.merge(u,v);
			extra += status[id];
			curr.pb(id);
		}

		int val = f(curr);
		return val-extra;
	};

	// find the status of all non-tree adj edges to u (s.t u < v)
	rep(u,n){
		vector<int> edges;
		for(auto [v,id] : adj[u]){
			if(status[id] != -1) conts;
			if(v < u) conts;
			edges.pb(id);
		}

		while(!edges.empty()){
			if(!get(edges)) break;
			int l = 0, r = sz(edges)-1;
			int first = -1;
			while(l <= r){
				int mid = (l+r) >> 1;
				vector<int> curr_edges;
				rep(i,mid+1) curr_edges.pb(edges[i]);
				
				if(get(curr_edges)){
					first = mid;
					r = mid-1;
				}
				else{
					l = mid+1;
				}
			}

			assert(first != -1);

			vector<int> nxt_edges;
			rep(i,sz(edges)){
				if(i < first){
					status[edges[i]] = 0;
				}
				else if(i == first){
					status[edges[i]] = 1;
				}
				else{
					nxt_edges.pb(edges[i]);
				}
			}

			edges = nxt_edges;
		}
	}

	vector<int> ans;
	rep(i,m){
		if(status[i] == 1){
			ans.pb(i);
		}
	}

	return ans;
}

• Subtask 1: 13 / 13
• Subtask 2: 0 / 17
• Subtask 3: 0 / 21
• Subtask 4: 19 / 19
• Subtask 5: 0 / 30