Submission #398690

#	Time	Username	Problem	Language	Result	Execution time	Memory
398690		ChrisT	Event Hopping 2 (JOI21_event2)	C++17	0 / 100	77 ms	25816 KiB

event2

#include <bits/stdc++.h>
using namespace std;
const int MN = 2e5 + 5, MOD = 1e9 + 7, LOG = 17;
int dp[MN], bit[MN], to[MN], p[MN][LOG];
vector<int> withDp[MN];
void update (int i, int v) {
	for (;i<MN;i+=i&-i)
		bit[i] = max(bit[i],v);
}
int query (int i) {
	int ret = 0;
	for (;i>0;i^=i&-i)
		ret = max(ret,bit[i]);
	return ret;
}
vector<int> xs;
int getx (int x) {return lower_bound(xs.begin(),xs.end(),x) - xs.begin() + 1;}
int main () {
	int n,k; scanf ("%d %d",&n,&k);
	vector<array<int,3>> segs(n+1);
	vector<array<int,2>> og(n+1);
	for (int i = 1; i <= n; i++) {
		auto &[l,r,idx] = segs[i];
		idx = i;
		scanf ("%d %d",&l,&r); og[i] = {l,r};
		xs.push_back(l); xs.push_back(r);
	}
	xs.push_back(0); xs.push_back(MOD);
	segs.push_back({0,0,n+1}); segs.push_back({MOD,MOD,n+2});
	n += 2;
	sort(xs.begin(),xs.end()); xs.erase(unique(xs.begin(),xs.end()),xs.end());
	sort(segs.begin()+1,segs.end());
	for (int i = 1; i <= n; i++) {
		auto &[l,r,idx] = segs[i];
		l = getx(l); r = getx(r); to[idx] = i;
		dp[i] = query(l) + 1;
		update(r,dp[i]);
		withDp[dp[i]].push_back(i);
	}
	int mx = *max_element(dp+1,dp+1+n);
	if (mx - 2 < k) return !printf ("-1\n");
	auto get = [&] (int v, int x) { //l[i] >= x
		int low = 0, high = (int)withDp[v].size() - 1, mid, ans = -1;
		while (low <= high) {
			mid = (low + high) / 2;
			if (segs[withDp[v][mid]][0] >= x) high = (ans = mid) - 1;
			else low = mid + 1;
		}
		assert(~ans);
		return withDp[v][ans];
	};
	for (int v = mx-1; v >= 1; v--) {
		int mn = 1e9;
		for (int j = (int)withDp[v].size() - 1; j >= 0; j--) {
			int i = withDp[v][j];
			mn = min(mn,segs[i][1]);
			p[i][0] = get(v+1,mn);
			for (int j = 1; j < LOG; j++)
				p[i][j] = p[p[i][j-1]][j-1];
		}
	}
	auto pathLength = [&] (int i, int j) { //i < j, dp[i] < dp[j]
		int ret = dp[j] - dp[i];
		for (int k = 0; k < LOG; k++) 
			if (ret >> k & 1) 
				i = p[i][k];
		return ret + (i <= j);
	};
	set<int> have = {1,n};
	int cur = dp[n] - 2;
	for (int j = 1; j <= n-2 && (int)have.size() < k + 2; j++) {
		int i = to[j];
		auto it = have.lower_bound(i);
		int lst = *prev(it), nxt = *it;
		if (segs[lst][1] > segs[i][0] || segs[i][1] > segs[nxt][0]) continue;
		int oldGet = pathLength(lst,nxt);
		int newGet = pathLength(lst,i) + pathLength(i,nxt) - 1;
		if (cur - oldGet + newGet >= k) { //success
			printf ("%d\n",j);
			have.insert(i);
			cur += newGet - oldGet;
		}
	}
	return 0;
}

Compilation message (stderr)

event2.cpp: In function 'int main()':
event2.cpp:19:17: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   19 |  int n,k; scanf ("%d %d",&n,&k);
      |           ~~~~~~^~~~~~~~~~~~~~~
event2.cpp:25:9: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   25 |   scanf ("%d %d",&l,&r); og[i] = {l,r};
      |   ~~~~~~^~~~~~~~~~~~~~~

• Subtask 1: 0 / 7
• Subtask 2: 0 / 1
• Subtask 3: 0 / 31
• Subtask 4: 0 / 61