Submission #724932

#	Time	Username	Problem	Language	Result	Execution time	Memory
724932		Rafi22	Alternating Current (BOI18_alternating)	C++14	0 / 100	38 ms	2352 KiB

alternating

#include <bits/stdc++.h>

using namespace std;

#define endl '\n'
#define st first
#define nd second
#define pb push_back
#define sz(x) (int)(x).size()
#define all(x) (x).begin(), (x).end()
#define ll long long
ll mod=1000000007;
int inf=1000000007;
ll infl=1000000000000000007;

void gg()
{
    cout<<"impossible";
    exit(0);
}

const int N=100007,pot=1<<17;

bool ans[N];
int l[N];
int r[N];
int ile[N];
int L[N];

pair<int,int> seg[2*pot+7];

void ins(int v,int x,int i)
{
    v+=pot-1;
    seg[v]=max(seg[v],{x,i});
    while(v>1)
    {
        v/=2;
        seg[v]=max(seg[2*v],seg[2*v+1]);
    }
}
pair<int,int>que(int v,int a,int b,int l,int r)
{
    if(a<=l&&b>=r) return seg[v];
    if(r<a||l>b) return {-inf,0};
    return max(que(2*v,a,b,l,(l+r)/2),que(2*v+1,a,b,(l+r)/2+1,r));
}

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int n,m;
    cin>>n>>m;
    int mx=0,k;
    for(int i=1;i<=m;i++)
    {
        cin>>l[i]>>r[i];
        l[i]--;
        r[i]--;
        if((r[i]-l[i]+n)%n+1>mx)
        {
            mx=(r[i]-l[i]+n)%n+1;
            k=i;
        }
    }
    ans[k]=1;
    int t=l[k];
    for(int i=1;i<=m;i++)
    {
        l[i]=(l[i]-t+n)%n;
        r[i]=(r[i]-t+n)%n;
        if(l[i]<=r[i])
        {
            ile[l[i]]++;
            ile[r[i]+1]--;
        }
        else
        {
            ile[l[i]]++;
            ile[0]++;
            ile[r[i]+1]--;
        }
    }
    int act=0;
    L[0]=-1;
    for(int i=0;i<n;i++)
    {
        act+=ile[i];
        if(act<2) gg();
        if(i>0) L[i]=L[i-1];
        if(act==2) L[i]=i;
    }
    set<pair<int,int>>is;
    is.insert({inf,0});
    for(int i=1;i<=m;i++)
    {
        cout<<l[i]<<" "<<r[i]<<endl;
        if(l[i]<=r[i]) ins(l[i]+1,r[i],i);
        else is.insert({l[i],i});
    }
    int a=0,b=r[k];
    while(true)
    {
        if(b==n-1) break;
        int x=L[b];
        a=max(a,x+1);
        if((*is.lower_bound({a,0})).st<=b+1)
        {
            ans[(*is.lower_bound({a,0})).nd]=1;
            break;
        }
        pair<int,int>p=que(1,a+1,b+2,1,pot);
        if(p.st<=b) gg();
        a=b+1;
        b=p.st;
        ans[p.nd]=1;
    }
    for(int i=1;i<=m;i++) cout<<ans[i];

    return 0;
}

Compilation message (stderr)

alternating.cpp: In function 'int main()':
alternating.cpp:68:11: warning: 'k' may be used uninitialized in this function [-Wmaybe-uninitialized]
   68 |     ans[k]=1;
      |     ~~~~~~^~

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