Submission #1225154

#	Time	Username	Problem	Language	Result	Execution time	Memory
1225154		_rain_	Railway Trip (JOI17_railway_trip)	C++20	100 / 100	77 ms	16584 KiB

railway_trip

#include<bits/stdc++.h>
using namespace std;
typedef long long LL;

const int N=(int)1e5;
const int MAXLOG=17;
	int source[N+2],sink[N+2],l[N+2];
	int rmq[N+2][MAXLOG+2][2];
	int LOG[N+2];
	int n,k,q;

int main(){
	ios::sync_with_stdio(false);
	cin.tie(0) ; cout.tie(0);
	#define task "main"
	if (fopen(task".inp","r")){
		freopen(task".inp","r",stdin);
		freopen(task".out","w",stdout);
	}
	
	cin>>n>>k>>q;
	for(int i=1;i<=n;++i) cin>>l[i];
		//... BUILDING RMQ
			vector<int>v;
			for(int i=1;i<=n;++i){
				while (v.size() && l[v.back()]<l[i]) v.pop_back();
				if (v.empty()) rmq[i][0][0]=1; else rmq[i][0][0]=v.back();
				v.push_back(i);
			}
			v.clear();
			for(int i=n;i>=1;--i){
				while (v.size() && l[v.back()]<l[i]) v.pop_back();
				if (v.empty()) rmq[i][0][1]=n; else rmq[i][0][1]=v.back();
				v.push_back(i);
			}

			for(int j=1;j<=MAXLOG;++j){
				for(int i=1;i<=n;++i){
					int l=rmq[i][j-1][0],r=rmq[i][j-1][1];
					rmq[i][j][0]=min(rmq[l][j-1][0],rmq[r][j-1][0]);
					rmq[i][j][1]=max(rmq[l][j-1][1],rmq[r][j-1][1]);
				}
			}
			
	while (q--){
		int source,sink;
		cin>>source>>sink;
		if (source>sink) swap(source,sink);
		int l,r,need;
		l=source,r=source,need=sink;
		LL ans=0;
		for(int i=MAXLOG;i>=0;--i){
			if (max(rmq[l][i][1],rmq[r][i][1])<need){
				ans+=(1<<i);
				int tmp_l=l,tmp_r=r;
				r=max(rmq[tmp_l][i][1],rmq[tmp_r][i][1]);
				l=min(rmq[tmp_l][i][0],rmq[tmp_r][i][0]);
			}
		}
		need=r,l=sink,r=sink;
		for(int i=MAXLOG;i>=0;--i){
			if (min(rmq[l][i][0],rmq[r][i][0])>need){
				ans+=(1<<i);
				int tmp_l=l,tmp_r=r;
				r=max(rmq[tmp_l][i][1],rmq[tmp_r][i][1]);
				l=min(rmq[tmp_l][i][0],rmq[tmp_r][i][0]);
			}
		}
		cout<<ans<<'\n';
	}
		
	return 0 ;
}

Compilation message (stderr)

railway_trip.cpp: In function 'int main()':
railway_trip.cpp:17:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   17 |                 freopen(task".inp","r",stdin);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
railway_trip.cpp:18:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   18 |                 freopen(task".out","w",stdout);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 15 / 15
• Subtask 3: 25 / 25
• Subtask 4: 55 / 55