#include <bits/stdc++.h>
using namespace std;
int main() {
int n, q;
cin >> n >> q;
vector<vector<int> > dp(17, vector<int>(n));
vector<vector<pair<int, int> > > sparseTables(17, vector<pair<int, int> >(n, make_pair(1000000001, -1)));
vector<pair<int, int> > a(n);
vector<int> b;
for (int i = 0; i < n; i++) {
cin >> a[i].first >> a[i].second;
b.push_back(a[i].second);
}
sort(b.begin(), b.end());
b.erase(unique(b.begin(), b.end()), b.end());
for (int i = 0; i < n; i++) {
int right = lower_bound(b.begin(), b.end(), a[i].second) - b.begin();
sparseTables[0][right] = min(sparseTables[0][right], make_pair(a[i].first, i));
}
for (int i = 0; i + 1 < 17; i++){
for (int j = 0; j + (1 << (i + 1)) <= n; j++){
sparseTables[i + 1][j] = min(sparseTables[i][j], sparseTables[i][j + (1 << i)]);
}
}
for (int i = 0; i < n; i++){
int left = lower_bound(b.begin(), b.end(), a[i].first) - b.begin();
int right = lower_bound(b.begin(), b.end(), a[i].second) - b.begin();
int h = 31 - __builtin_clz(right - left + 1);
dp[0][i] = min(sparseTables[h][left], sparseTables[h][right + 1 - (1 << h)]).second;
}
for (int i = 0; i + 1 < 17; i++){
for (int j = 0; j < n; j++){
dp[i + 1][j] = dp[i][dp[i][j]];
}
}
while (q--) {
int x, y;
int left = 1;
cin >> x >> y;
x--;
y--;
if (x == y || (a[y].first <= a[x].second && a[x].second <= a[y].second)) {
cout << (x == y ? 0 : 1) << "\n";
continue;
}
for (int i = 17 - 1; ~i; i--) {
if (a[x].second < a[arr[i][y]].first){
left += 1 << i, y = dp[i][y];
}
}
y = dp[0][y];
if (a[x].second < a[y].first || a[x].second > a[y].second){
cout << "impossible\n";
}
else{
cout << left + (a[x].second >= a[y].first) << "\n";
}
}
}
Compilation message
events.cpp: In function 'int main()':
events.cpp:47:33: error: 'arr' was not declared in this scope
47 | if (a[x].second < a[arr[i][y]].first){
| ^~~
