This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include <bits/stdc++.h>
using namespace std;
struct query
{
int l,r,i;
query(){}
query(int _l,int _r,int _i)
{
l=_l;
r=_r;
i=_i;
}
};
struct edge
{
int x,y;
edge(){}
edge(int _x,int _y)
{
x=_x;
y=_y;
}
};
int n,m,k;
query a[200001];
pair<int,int> e[200001],q[200001];
void read()
{
cin>>n>>m>>k;
for(int i=1;i<=m;i++)
{
int x,y;
cin>>x>>y;
e[i]={x,y};
}
for(int i=1;i<=k;i++)
{
int l,r;
cin>>l>>r;
q[i]={l,r};
a[i]={l,r,i};
}
}
int used[200001];
vector<int> v[200001];
bool pos;
void dfs(int i)
{
for(int j=0;j<v[i].size();j++)
{
int nb=v[i][j];
if(!used[nb])
{
used[nb]=1;
if(used[i]==1)used[nb]=2;
dfs(nb);
}
else if(used[i]==used[nb])pos=0;
}
}
void slow()
{
for(int i=1;i<=k;i++)
{
pos=1;
for(int j=1;j<=n;j++)
{
used[j]=0;
v[j].clear();
}
for(int j=1;j<q[i].first;j++)
{
v[e[j].first].push_back(e[j].second);
v[e[j].second].push_back(e[j].first);
}
for(int j=q[i].second+1;j<=m;j++)
{
v[e[j].first].push_back(e[j].second);
v[e[j].second].push_back(e[j].first);
}
for(int j=1;j<=n;j++)
{
if(!used[j])
{
used[j]=1;
dfs(j);
}
}
if(pos)cout<<"NO"<<endl;
else cout<<"YES"<<endl;
}
}
int minr[200001];
int sz[200001];
pair<int,int> p[200001];
void init()
{
pos=1;
for(int i=1;i<=n;i++)
p[i]={i,0},sz[i]=1;
}
pair<int,int> parent(int x)
{
if(x==p[x].first)return p[x];
int curr=p[x].second;
p[x]=parent(p[x].first);
p[x].second+=curr;
return p[x];
}
void unite(int x,int y)
{
pair<int,int> pxx=parent(x);
pair<int,int> pyy=parent(y);
int px=pxx.first;
int py=pyy.first;
if(px!=py)
{
if(sz[px]>sz[py])swap(px,py);
p[px]={py,pxx.second+1+pyy.second};
sz[py]+=sz[px];
}
else
{
//cout<<x<<" "<<y<<" "<<pxx.second<<" "<<pyy.second<<endl;
if(pxx.second%2==pyy.second%2)
pos=0;
}
}
void subt()
{
for(int i=1;i<=min(200,m);i++)
{
//cout<<i<<endl;
init();
for(int j=1;j<i;j++)
{
unite(e[j].first,e[j].second);
if(pos==0)
{
//cout<<"in"<<" "<<i<<" "<<j<<endl;
minr[i]=m+1;
break;
}
}
for(int j=m;j>i;j--)
{
unite(e[j].first,e[j].second);
if(pos==0)
{
//cout<<"in"<<" "<<i<<" "<<j<<endl;
minr[i]=max(minr[i],j);
break;
}
}
}
for(int i=1;i<=k;i++)
{
if(minr[q[i].first]>q[i].second)cout<<"YES"<<endl;
else cout<<"NO"<<endl;
}
}
int s;
bool cmp(query q1,query q2)
{
int b1=q1.l/s;
int b2=q2.l/s;
if(q1.l%s!=0)b1++;
if(q2.l%s!=0)b2++;
if(b1==b2)return q1.r>q2.r;
return q1.l<q2.l;
}
stack<pair<int,int> > st;
int cnt1,cnt2;
pair<int,int> parent2(int x)
{
if(p[x].first==x)return p[x];
pair<int,int> h=parent2(p[x].first);
h.second+=p[x].second;
return h;
}
void unite2(int x,int y,int&cnt)
{
//cout<<x<<" + "<<y<<endl;
pair<int,int> pxx=parent2(x);
pair<int,int> pyy=parent2(y);
int px=pxx.first;
int py=pyy.first;
if(px!=py)
{
if(sz[px]>sz[py])swap(px,py);
p[px]={py,pxx.second+pyy.second+1};
sz[py]+=sz[px];
st.push({px,py});
cnt++;
//cout<<"in"<<endl;
}
else
{
if(pxx.second%2==pyy.second%2)
{
pos=1;
//cout<<"fing"<<endl;
}
}
}
int nun;
void rollback()
{
pair<int,int> h=st.top();
st.pop();
//cout<<h.first<<" - "<<h.second<<endl;
sz[h.second]-=sz[h.first];
p[h.first]={h.first,0};
}
int ans[200001];
bool mark;
void small()
{
init();
s=sqrt(m);
sort(a+1,a+k+1,cmp);
int bg=1;
int curr=m;
int pr=0;
int all=0;
pos=0;
for(int i=1;i<=k;i++)
{
//cout<<i<<"!"<<" "<<all<<endl;
if(all==1)
{
ans[a[i].i]=1;
continue;
}
int b=a[i].l/s;
if(a[i].l%s!=0)b++;
//cout<<"i "<<a[i].l<<" "<<b<<endl;
if(pr!=b)
{
if(mark)pos=0,mark=0;;
while(cnt2)
{
cnt2--;
rollback();
}
bool pc=pos;
for(int j=bg;j<=(b-1)*s;j++)
{
//cout<<"added "<<j<<endl;
unite2(e[j].first,e[j].second,nun);
}
if(pos)all=1;
bg=(b-1)*s;
pr=b;
}
bool pc1=pos;
while(curr>a[i].r)
{
unite2(e[curr].first,e[curr].second,cnt2);
curr--;
}
//cout<<pos<<endl;
if(pos==1&&pc1==0)mark=1;
bool pc=pos;
for(int j=b*(s-1)+1;j<a[i].l;j++)
unite2(e[j].first,e[j].second,cnt1);
if(pos)ans[a[i].i]=1;
while(cnt1)
{
cnt1--;
rollback();
}
if(pos!=pc)pos=pc;
}
for(int i=1;i<=k;i++)
if(ans[i])cout<<"YES"<<endl;
else cout<<"NO"<<endl;
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
read();
if(k<=2000)small();
else if(n<=2000)slow();
else subt();
//slow();
return 0;
}
/*
6 8 2
1 3
1 5
1 6
2 5
2 6
3 4
3 5
5 6
1 3
4 7
*/
Compilation message (stderr)
Joker.cpp: In function 'void dfs(int)':
Joker.cpp:56:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
56 | for(int j=0;j<v[i].size();j++)
| ~^~~~~~~~~~~~
Joker.cpp: In function 'void small()':
Joker.cpp:285:18: warning: unused variable 'pc' [-Wunused-variable]
285 | bool pc=pos;
| ^~
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