Submission #648847

#	Time	Username	Problem	Language	Result	Execution time	Memory
648847		fatemetmhr	Alternating Current (BOI18_alternating)	C++17	19 / 100	38 ms	18176 KiB

alternating

// ~ Be Name Khoda ~

// Harf ke nazanim... 
// Zende bemoonim?
// Ya oonm na?


#include<bits/stdc++.h>

using namespace std;

typedef long long ll;

#define pb       push_back
#define mp       make_pair
#define all(x)   x.begin(), x.end()
#define fi       first
#define se       second

const int maxn  =  1e6   + 10;
const int maxn5 =  5e5   + 10;
const int maxnt =  1.2e6 + 10;
const int maxn3 =  1e3   + 10;
const int mod   =  1e9   +  7;
const ll  inf   =  1e18;

int a[maxn5], b[maxn5];
bool have[2][maxn5];
int n, m;
bool ty[maxn5], mark[maxn5];
vector <int> seg[maxn5], ex;


inline void solve(){
    for(int i = 0; i < n; i++)
        seg[i].clear();
    ex.clear();
    for(int i = 0; i < m; i++) if(!mark[i]){
        seg[a[i] > b[i] ? 0 : a[i]].pb(i);
    }
    int id1 = -1, id2 = -1;
    for(int i = 0; i < n; i++){
        if(id1 != -1 && b[id1] < i)
            id1 = -1;
        if(id2 != -1 && b[id2] < i)
            id2 = -1;
        //cout << "here we go " << i << ' ' << id1 << ' ' << id2 << ' ' << have[1][i] << ' ' << have[0][i] << endl;
        while(!ex.empty() && b[ex.back()] < i)
            ex.pop_back();
        for(auto u : seg[i])
            ex.pb(u);
        if(id1 == -1 && !have[1][i]){
            if(ex.empty())
                return;
            id1 = ex.back();
            ty[id1] = true;
            ex.pop_back();
        }
        while(!ex.empty() && b[ex.back()] < i)
            ex.pop_back();
        if(id2 == -1 && !have[0][i]){
            if(ex.empty())
                return;
            id2 = ex.back();
            ty[id2] = false;
            ex.pop_back();
        }
    }
    for(int i = 0; i < m; i++)
        cout << ty[i];
    cout << endl;
    exit(0);
}


int main(){
    ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);

    cin >> n >> m;
    for(int i = 0; i < m; i++){
        cin >> a[i] >> b[i];
        a[i]--;
        b[i]--;
    }

    int blid = -1;

    for(int i = 0; i < m; i++) if(a[i] == 0 || a[i] > b[i])
        if(blid == -1 || a[blid] == 0 || a[blid] > a[i])
            blid = i;
    if(blid == -1){
        cout << "impossible\n";
        return 0;
    }

    //cout << "ok " << blid << endl;

    for(int i = 0; i < m; i++) if(i != blid && (a[i] == 0 || a[i] > b[i])){
        //cout << "check out " << i << ' ' << "wtf " << blid << endl;
        memset(mark, false, sizeof mark);
        mark[i] = true; ty[i] = 0; mark[blid] = true; ty[blid] = 1;
        memset(have, false, sizeof have);
        for(int j = a[i]; j != b[i]; j = (j + 1) % n)
            have[0][j] = true;
        have[0][b[i]] = true;
        int rbl = b[blid];
        for(int j = 0; j < m; j++) if(a[j] > b[j] && (a[i] == 0 || a[j] < a[i])){
            mark[j] = true; ty[j] = 1;
            rbl = max(rbl, b[j]);
            //cout << "blue forces " << j << endl;
        }
        for(int j = a[blid]; j != rbl; j = (j + 1) % n)
            have[1][j] = true;
        have[1][rbl] = true;
        solve();
    }

    cout << "impossible" << '\n';

}

• Subtask 1: 0 / 13
• Subtask 2: 0 / 20
• Subtask 3: 0 / 22
• Subtask 4: 19 / 19
• Subtask 5: 0 / 26