#include <bits/stdc++.h>
using namespace std;
#define all(a) a.begin(),a.end()
#define owo ios_base::sync_with_stdio(0);cin.tie(0);
const int MAXN = 1e5+1;
int s[MAXN],e[MAXN];
//fuck binlift how
//p(k,i) = min s if we jump backwards 2^k times
//p(k-1,i) = min of p(k-1),i<= x <= i ,p(k-1,x)
//yeesh but this n log^2n
//should pass maybe?
//1e5 * 18 * 18 = 3e7
int p[19][MAXN];
typedef pair<int,int> pii;
#define fi first
#define se second
pii T[8*MAXN];
pii mn[2*MAXN];
void build(int v,int l,int r){
if(l==r){
T[v] = mn[l];
return;
}
int tm = (l+r)/2;
build(2*v,l,tm);
build(2*v+1,tm+1,r);
T[v] = min(T[2*v],T[2*v+1]);
}
int main()
{
owo
int n,q;
cin>>n>>q;
vector<int>crd;
for(int i=0;i<n;i++)cin>>s[i]>>e[i];
for(int i=0;i<n;i++){
crd.push_back(s[i]);
crd.push_back(e[i]);
}
sort(all(crd));
crd.resize(unique(all(crd)) - crd.begin());
for(int i=0;i<n;i++){
s[i] = lower_bound(all(crd),s[i]) - crd.begin()+1;
e[i] = lower_bound(all(crd),e[i]) - crd.begin()+1;
}
int m = crd.size();
for(int i=1;i<=m;i++)mn[i] = {i,-1};
for(int i=0;i<n;i++)mn[e[i]] = min(mn[e[i]],{s[i],i});
build(1,1,m);
for(int i=0;i<n;i++){
p[0][i] = i;
pii res = query(1,s[i],e[i],1,m);
if(res.se != -1)p[0][i] = res.se;
}
for(int i=1;i<=18;i++){
for(int j=0;j<n;j++){
p[i][j] = p[i-1][p[i-1][j]];
}
}
while(q--){
int l,r;
cin>>l>>r;
l--;
r--;
if(l==r){
cout<<0<<'\n';
continue;
}
if(e[l] > e[r]){
cout<<"impossible"<<'\n';
continue;
}
if(s[r] <= e[l]){
cout<<1<<'\n';
continue;
}
int ans = 1; //one for actually arrivinf at l
/*
while(s[r] > e[l]){
if(p[0][r] == r){
ans = -1;
break;
}
ans++;
r = p[0][r];
}*/
for(int i=18;i>=0;i--){
int v = p[i][r];
if(s[v] > e[l]){
r = v;
ans+=(1<<i);
}
}
ans++;
if(r == p[0][r])ans=-1;
if(ans==-1)cout<<"impossible"<<'\n';
else cout<<ans<<'\n';
}
}
Compilation message
events.cpp: In function 'int main()':
events.cpp:53:13: error: 'query' was not declared in this scope
53 | pii res = query(1,s[i],e[i],1,m);
| ^~~~~
