#include<bits/stdc++.h>
using namespace std;
const int maxn = 1e5 + 10;
struct interval
{
int s, e, idx;
}seg[maxn];
struct query
{
int start, finish, idx;
}task[maxn];
bool cmp_finish(query q1, query q2)
{
return q1.finish < q2.finish;
}
int n, q;
void input()
{
cin >> n >> q;
for (int i = 1; i <= n; i ++)
{
cin >> seg[i].s >> seg[i].e;
seg[i].idx = i;
}
for (int i = 1; i <= q; i ++)
{
cin >> task[i].start >> task[i].finish;
task[i].idx = i;
}
}
bool cmp_end(interval seg1, interval seg2)
{
return seg1.e < seg2.e;
}
int lf[maxn], rev[maxn], rf[maxn], ans[maxn];
map < int, int > fix;
void build_graph()
{
sort(seg + 1, seg + n + 1, cmp_end);
for (int i = 1; i <= n; i ++)
{
rev[seg[i].idx] = i;
}
for (int i = 1; i <= n; i ++)
{
int l = 1;
int r = i;
while(l <= r)
{
int m = (l + r) / 2;
if (seg[m].e < seg[i].s)
l = m + 1;
else
r = m - 1;
}
lf[i] = l;
//while(seg[lf[i]].e < seg[i].s)
// lf[i] ++;
if (fix[seg[i].e] == 0)
fix[seg[i].e] = lf[i];
else
fix[seg[i].e] = min(fix[seg[i].e], lf[i]);
}
}
const int maxlog = 21;
int dp[maxlog][maxn];
void answer_queries()
{
for (int i = 1; i <= q; i ++)
{
task[i].start = rev[task[i].start];
task[i].finish = rev[task[i].finish];
}
sort(task + 1, task + q + 1, cmp_finish);
/**cout << "----------------------" << endl;
for (int i = 1; i <= n; i ++)
cout << seg[i].s << " :: " << seg[i].e << endl;*/
vector < int > viable;
int pt = 1;
for (int i = 1; i <= q; i ++)
{
int st = task[i].start, en = task[i].finish;
while(pt <= en)
{
while(!viable.empty() && lf[viable.back()] >= lf[pt])
viable.pop_back();
int l = 0, r = (int)(viable.size()) - 1;
while(l <= r)
{
int m = (l + r) / 2;
if (viable[m] < lf[pt])
l = m + 1;
else
r = m - 1;
}
if (l >= viable.size())
dp[0][pt] = pt;
else
dp[0][pt] = viable[l];
for (int j = 1; j < maxlog; j ++)
{
dp[j][pt] = dp[j - 1][dp[j - 1][pt]];
}
viable.push_back(pt);
pt ++;
}
if (st == en)
{
ans[task[i].idx] = 0;
continue;
}
if (seg[st].e == seg[en].e && st != en)
{
ans[task[i].idx] = 1;
continue;
}
if (st > en)
{
ans[task[i].idx] = -1;
continue;
}
if (st >= lf[en])
{
ans[task[i].idx] = 1;
continue;
}
int to = fix[seg[en].e];
for (int i = lf[en]; i <= en; i ++)
to = min(to, lf[i]);
int steps = 1;
bool done = false;
int cur = viable.size() - 1;
while(cur >= 0 && viable[cur] >= to)
cur --;
cur ++;
if (lf[viable[cur]] >= to)
{
ans[task[i].idx] = -1;
continue;
}
steps ++;
int jump = 0, ver = viable[cur];
if (st >= lf[ver])
{
ans[task[i].idx] = steps + 1;
continue;
}
///cout << "here " << task[i].idx << endl;
for (int bit = maxlog - 1; bit >= 0; bit --)
{
if (lf[dp[bit][ver]] > st)
{
ver = dp[bit][ver];
jump |= (1 << bit);
}
}
jump ++;
ver = dp[0][ver];
if (st >= lf[ver])
{
///cout << "HERE " << task[i].idx << endl;
ans[task[i].idx] = steps + jump + 1;
}
else
{
ans[task[i].idx] = -1;
}
}
for (int i = 1; i <= q; i ++)
{
if (ans[i] != - 1)
cout << ans[i] << endl;
else
cout << "impossible" << endl;
}
}
void solve()
{
input();
build_graph();
answer_queries();
}
int main()
{
///speed();
solve();
return 0;
}
Compilation message
events.cpp: In function 'void answer_queries()':
events.cpp:117:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
117 | if (l >= viable.size())
| ~~^~~~~~~~~~~~~~~~
events.cpp:161:14: warning: unused variable 'done' [-Wunused-variable]
161 | bool done = false;
| ^~~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
2 ms |
10588 KB |
Output is correct |
| 2 |
Correct |
256 ms |
18356 KB |
Output is correct |
| 3 |
Correct |
266 ms |
21196 KB |
Output is correct |
| 4 |
Incorrect |
280 ms |
21136 KB |
Output isn't correct |
| 5 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
1 ms |
10588 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
1 ms |
10588 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
1 ms |
10588 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
278 ms |
18264 KB |
Output is correct |
| 2 |
Correct |
269 ms |
21068 KB |
Output is correct |
| 3 |
Incorrect |
278 ms |
21136 KB |
Output isn't correct |
| 4 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
2 ms |
10588 KB |
Output is correct |
| 2 |
Correct |
256 ms |
18356 KB |
Output is correct |
| 3 |
Correct |
266 ms |
21196 KB |
Output is correct |
| 4 |
Incorrect |
280 ms |
21136 KB |
Output isn't correct |
| 5 |
Halted |
0 ms |
0 KB |
- |
