Submission #813862

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Source Code Expand

#include <bits/stdc++.h>

#define _overload(_1,_2,_3,name,...) name
#define _rep(i,n) _range(i,0,n)
#define _range(i,a,b) for(int i=int(a);i<int(b);++i)
#define rep(...) _overload(__VA_ARGS__,_range,_rep,)(__VA_ARGS__)

#define _rrep(i,n) _rrange(i,n,0)
#define _rrange(i,a,b) for(int i=int(a)-1;i>=int(b);--i)
#define rrep(...) _overload(__VA_ARGS__,_rrange,_rrep,)(__VA_ARGS__)

#define _all(arg) begin(arg),end(arg)
#define uniq(arg) sort(_all(arg)),(arg).erase(unique(_all(arg)),end(arg))
#define getidx(ary,key) lower_bound(_all(ary),key)-begin(ary)
#define clr(a,b) memset((a),(b),sizeof(a))
#define bit(n) (1LL<<(n))
#define popcount(n) (__builtin_popcountll(n))

template<class T>bool chmax(T &a, const T &b) { return (a<b)?(a=b,1):0;}
template<class T>bool chmin(T &a, const T &b) { return (b<a)?(a=b,1):0;}

using namespace std;

const int dx[8]={1,0,-1,0,1,-1,-1,1};
const int dy[8]={0,1,0,-1,1,1,-1,-1};

int n,m;

using state=pair<int,int>;
vector<state> ary;

const int nmax=200000;
int nxt[nmax][20];

int main(void){
	cin >> n >> m;
	rep(i,n){
		int s,t;
		cin >> s >> t;
		if(s>t) t+=m;
		ary.push_back(state(t,s));
		ary.push_back(state(t+m,s+m));
	}

	sort(_all(ary));

	int cur=0,tar=0;
	const int all=2*n;
	while(cur<all){
		while(tar<all && ary[tar].second<ary[cur].first) tar++;
		nxt[cur++][0]=tar;
	}


	rep(k,20)rep(i,2*n){
		if(nxt[i][k]==all)
			nxt[i][k+1]=all;
		else
			nxt[i][k+1]=nxt[nxt[i][k]][k];
	}

	int ans=0;

	rep(i,2*n){
		int s=ary[i].second,cur=i,num=1;
		rrep(k,20){
			int tar=nxt[cur][k];
			if(tar!=all && ary[tar].first<=s+m){
				cur=tar;
				num+=1<<k;
			}
		}
		chmax(ans,num);
	}

	cout << ans << endl;
	return 0;
}

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