Submission #720623

#	Time	Username	Problem	Language	Result	Execution time	Memory
720623		Jarif_Rahman	Simurgh (IOI17_simurgh)	C++17	100 / 100	1413 ms	6040 KiB

simurgh

#include "simurgh.h"
#include <bits/stdc++.h>
#define pb push_back
#define f first
#define sc second
using namespace std;
typedef long long int ll;
typedef string str;

struct dsu{
    int n;
    vector<int> sz, p;
    dsu(int _n): n(_n){
        sz.resize(n, 1);
        p.resize(n);
        for(int i = 0; i < n; i++) p[i] = i;
    }
    int get(int x){
        if(p[x] != x) p[x] = get(p[x]);
        return p[x];
    }
    bool unite(int a, int b){
        a = get(a), b  = get(b);
        if(a == b) return 0;
        if(sz[b] > sz[a]) swap(a, b);
        sz[a]+=sz[b];
        sz[b] = 0;
        p[b] = a;
        return 1;
    }
};

int n, m;
vector<int> U, V;
vector<int> royal;
vector<vector<pair<int, int>>> graph;

int count_common_roads(const basic_string<int>& E){
    vector<int> EE;
    for(int x: E) EE.pb(x);
    return count_common_roads(EE);
}
basic_string<int> generate_tree(const basic_string<int>& E){
    dsu ds(n);
    basic_string<int> T;
    for(int i: E){
        if(ds.unite(U[i], V[i])) T.pb(i);
        else return {};
    }
    for(int i = 0; i < m; i++) if(ds.unite(U[i], V[i])) T.pb(i);
    return T;
}
pair<basic_string<int>,basic_string<int>> forcefully_generate_tree(const basic_string<int>& E){
    dsu ds(n);
    basic_string<int> T, I;
    for(int i: E){
        if(ds.unite(U[i], V[i])) T.pb(i);
        else I.pb(i);
    }
    for(int i = 0; i < m; i++) if(ds.unite(U[i], V[i])) T.pb(i);
    return {T, I};
}
int replacement_edge(const basic_string<int>& E, int i){
    dsu ds(n);
    for(int j: E) if(j != i) ds.unite(U[j], V[j]);
    for(int j = 0; j < m; j++) if(j != i && ds.unite(U[j], V[j])) return j;
    return -1;
}
int count_extra_royal(const basic_string<int>& T, basic_string<int> C){
    dsu ds(n);
    int c = 0;
    vector<int> q;
    for(int i: C) ds.unite(U[i], V[i]), q.pb(i);
    for(int i: T) if(ds.unite(U[i], V[i])) c+=max(royal[i], 0), q.pb(i);
    return count_common_roads(q)-c;
}

vector<int> find_roads(int _n, vector<int> _U, vector<int> _V){
    swap(n, _n), swap(U, _U), swap(V, _V);
    m = U.size();
    royal.assign(m, -1);
    graph.resize(n);

    for(int i = 0; i < m; i++){
        graph[U[i]].pb({V[i], i});
        graph[V[i]].pb({U[i], i});
    }

    basic_string<int> A, B = {0};
    while(1){
        int x, y, z;
        int ei = int(A.size()+B.size())-1, e = B.back();

        if(A.size()+B.size() == n-1){
            int cnt = 0;
            for(int i: A) if(royal[i] == 1) cnt++;
            int x = count_common_roads(A+B);
            A+=B;
            for(int i: B) royal[i] = (x > cnt);
            break;
        }

        auto T = generate_tree(A+B);
        int i = replacement_edge(T, e);

        if(i == -1){
            for(int j: B) royal[j] = 1;
            goto finalize;
        }
        x = count_common_roads(T);
        T[ei] = i;
        y = count_common_roads(T);
        T[ei] = e;

        if(x > y){
            for(int j: B) royal[j] = 1;
            royal[i] = 0;
            goto finalize;
        }
        else if(x < y){
            for(int j: B) royal[j] = 0;
            royal[i] = 1;
            goto finalize;
        }
        else{
            if(royal[i] != -1){
                for(int j: B) royal[j] = royal[i];
                goto finalize;
            }
            if(generate_tree(A+B+i).empty()){
                if(generate_tree(B+i).empty()){
                    for(int j: B) royal[j] = 0;
                    royal[i] = 0;
                    goto finalize;
                }
                auto [T2, I] = forcefully_generate_tree(B+i+A);
                z = count_common_roads(T2);
                if(z > x){
                    for(int j: B) royal[j] = 1;
                }
                else if(z < x){
                    for(int j: B) royal[j] = 0;
                }
                else{
                    for(int j: B) royal[j] = royal[I[0]];
                }
                goto finalize;
            }
            else{
                B.pb(i);
                continue;
            }
        }

        finalize:
        A+=B;
        B.clear();
        if(A.size() + B.size() == n-1) break;
        B+=T[A.size()+B.size()];
    }

    vector<int> ans;
    for(int i = 0; i < m; i++) if(royal[i] == 1) ans.pb(i);

    for(int nd = 0; nd < n; nd++){
        basic_string<int> S;
        for(auto [x, i]: graph[nd]) if(royal[i] == -1) S.pb(i);
        if(S.empty()) continue;
        int X = count_extra_royal(A, S);
        while(X > 0){
            int a = 1, b = S.size();
            while(a < b){
                int md = (a+b)/2;
                if(count_extra_royal(A, S.substr(0, md)) >= X) b = md;
                else a = md+1;
            }
            royal[S[a-1]] = 1;
            ans.pb(S[a-1]);
            X--;
        }
        for(int i: S) if(royal[i] == -1) royal[i] = 0;
    }

    return ans;
}

Compilation message (stderr)

simurgh.cpp: In function 'std::vector<int> find_roads(int, std::vector<int>, std::vector<int>)':
simurgh.cpp:94:30: warning: comparison of integer expressions of different signedness: 'std::__cxx11::basic_string<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   94 |         if(A.size()+B.size() == n-1){
      |            ~~~~~~~~~~~~~~~~~~^~~~~~
simurgh.cpp:158:32: warning: comparison of integer expressions of different signedness: 'std::__cxx11::basic_string<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
  158 |         if(A.size() + B.size() == n-1) break;
      |            ~~~~~~~~~~~~~~~~~~~~^~~~~~

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