Submission #1093669

#	Time	Username	Problem	Language	Result	Execution time	Memory
1093669		duyhoanho	Joker (BOI20_joker)	C++14	39 / 100	95 ms	22132 KiB

Joker

#include<bits/stdc++.h>
#define int long long
#define forinc(i,a,b) for(int i=a;i<=b;i++)
#define fi first
#define se second
#define pii pair<int,int>
#define pb push_back
using namespace std;
const int N = 2e5+10;
int n,m,q,fre[N],lz[N],p[N],sz[N];
int ans[N];
pii d[N];
vector<int> ad[N];
//sub1
bool qu1(int l,int r)
{
    bool ok = 0;
    forinc(i,1,n) ad[i].clear();
    forinc(i,1,m)
    {
        if(l<=i && i<=r) continue;
        int x,y;
        tie(x,y) = d[i];
        ad[x].pb(y);
        ad[y].pb(x);
    }

    for(int i=1; i<=n; i++) fre[i] = -1;
    for(int i=1; i<=n; i++)
    {
        if(fre[i] == -1)
        {
            queue<int> q;
            q.push(i);
            fre[i] = 0;
            while(q.size())
            {
                int u = q.front();
                q.pop();
                for(int v:ad[u])
                {
                    if(fre[v] == fre[u]) return true;
                    if(fre[v] != -1) continue;
                    fre[v] = 1 - fre[u];
                    q.push(v);
                }

            }
        }
    }
    return false;
}
//sub2
struct node
{
  int l,r,id;
}qu[N];
bool cmp(node a,node b)
{
  return a.r > b.r;
}
int pa(int v,int &c)
{
    c ^= lz[v];
    if(p[v] == v) return v;
    return pa(p[v], c);
}
void join(int a,int b)
{
    int ca = 0;
    int cb = 0;
    a = pa(a,ca);
    b = pa(b,cb);
    if(a != b)
    {
        if(sz[a] < sz[b]) swap(a,b);
        sz[a] += sz[b];
        p[b] = a;
        if(ca == cb) lz[b] = 1;
    }
}
bool check(int a,int b)
{
    int ca = 0;
    int cb = 0;
    a = pa(a,ca);
    b = pa(b,cb);
    if(a == b && ca == cb) return true;
    return false;
}
//bool qu2(int l,int r)
//{
//    for(int i=1; i<=m; i++)
//    {
//        if(l<=i && i<=r) continue;
//        if(check(d[i].fi, d[i].se)) return true;
//        join(d[i].fi, d[i].se);
//    }
//    return false;
//}
int32_t main()
{
    if(fopen("task.inp","r"))
    {
        freopen("task.inp","r",stdin);
        freopen("task.out","w",stdout);
    }
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cin>>n>>m>>q;
    forinc(i,1,m)
    {
        int x,y;
        cin>>x>>y;
        d[i] = {x,y};
    }
    if(n<=2000 && m <= 2000 && q <= 2000)
    {
        while(q--)
        {
            int l,r;
            cin>>l>>r;
            cout<< (qu1(l,r) ? "YES\n" : "NO\n");
        }
        return 0;

    }
    forinc(i,1,n)
    {
        sz[i] = 1;
        p[i] = i;
        lz[i] = 0;
    }

    forinc(i,1,q)
    {
        int l,r;
        cin>>l>>r;
        qu[i] = {l,r,i};
    }
    sort(qu + 1 , qu + q + 1,cmp);
    bool ok=0;
    for(int i = m; i>qu[1].r ;i--)
    {
      if(check(d[i].fi , d[i].se)) ok=1;
      join(d[i].fi,d[i].se);
    }
    ans[qu[1].id] = ok;
    for(int i=2;i<=q;i++)
    {
      for(int j = qu[i-1].r;j>qu[i].r;j--)
      {
        if(check(d[j].fi,d[j].se)) ok = 1;
        join(d[j].fi , d[j].se);
      }
      ans[qu[i].id] = ok;
    }
    forinc(i,1,q) cout<<(ans[i] ? "YES\n" : "NO\n");
}

Compilation message (stderr)

Joker.cpp: In function 'bool qu1(long long int, long long int)':
Joker.cpp:17:10: warning: unused variable 'ok' [-Wunused-variable]
   17 |     bool ok = 0;
      |          ^~
Joker.cpp: In function 'int32_t main()':
Joker.cpp:105:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  105 |         freopen("task.inp","r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
Joker.cpp:106:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  106 |         freopen("task.out","w",stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 6 / 6
• Subtask 2: 8 / 8
• Subtask 3: 25 / 25
• Subtask 4: 0 / 10
• Subtask 5: 0 / 22
• Subtask 6: 0 / 29