Submission #211806

#	Time	Username	Problem	Language	Result	Execution time	Memory
211806		username	Building 4 (JOI20_building4)	C++14	100 / 100	352 ms	52076 KiB

building4

#pragma GCC optimize("Ofast,unroll-loops,no-stack-protector")
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>
#include<ext/rope>
using namespace __gnu_pbds;
using namespace __gnu_cxx;
#define tr(it,a) for(auto it:a)
#define pob pop_back
#define pf push_front
#define pof pop_front
#define umin(x,y) (x=min(x,(y)))
#define umax(x,y) (x=max(x,(y)))
#define mid ((l+r)/2)
#define lch (idx*2+1)
#define rch (idx*2+2)
//
#include<bits/stdc++.h>
#define int int_fast64_t
using namespace std;
typedef pair<int,int> pii;
#define REP(i,j,k) for(int i=(j);i<(k);++i)
#define RREP(i,j,k) for(int i=int(j)-1;i>=(k);--i)
#define ALL(a) a.begin(),a.end()
#define pb push_back
#define f first
#define s second
#define endl '\n'
// #define __db
#ifdef __db
	#define IOS
	#define prt(...) cerr<<__VA_ARGS__
	#define ary(s,t)\
		for(auto it=(s);it!=(t);++it)prt(*it<<" ");\
		prt(endl);
#else
	#define IOS cin.tie(0),cout.tie(0),ios_base::sync_with_stdio(false)
	#define prt(...)
	#define ary(...)
#endif
//
const int maxn=1e6+9,inf=1ll<<60;
int n,m,a[maxn][2];
pii dp[maxn][2];
string s;

pii merge(pii x,pii y){
	if(x.f<0)return y;
	else if(y.f<0)return x;
	else return {min(x.f,y.f),max(x.s,y.s)};
}

main(){
	IOS;
	cin>>n,m=n<<1;
	REP(i,0,2)REP(j,0,m)cin>>a[j][i];
	dp[0][0]={0,0};
	dp[0][1]={1,1};
	REP(i,1,m){
		REP(j,0,2){
			dp[i][j]={-inf,-inf};
			if(a[i-1][0]<=a[i][j]){
				pii tt=dp[i-1][0];
				tt.f+=j,tt.s+=j;
				dp[i][j]=merge(dp[i][j],tt);
			}
			if(a[i-1][1]<=a[i][j]){
				pii tt=dp[i-1][1];
				tt.f+=j,tt.s+=j;
				dp[i][j]=merge(dp[i][j],tt);
			}
		}
	}
	pii tt={m-1,0},x=dp[tt.f][tt.s];
	if(n<x.f||x.s<n){
		tt.s=1,x=dp[tt.f][tt.s];
		if(n<x.f||x.s<n)return cout<<-1<<endl,0;
	}
	s+='A'+tt.s;
	int c=n-tt.s;
	while(tt.f){
		REP(i,0,2){
			if(a[tt.f-1][i]<=a[tt.f][tt.s]&&dp[tt.f-1][i].f<=c&&c<=dp[tt.f-1][i].s){
				tt={tt.f-1,i};
				c-=i;
				break;
			}
		}
		s+='A'+tt.s;
	}
	reverse(ALL(s));
	cout<<s<<endl;
}

Compilation message (stderr)

building4.cpp:52:6: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
 main(){
      ^

• Subtask 1: 11 / 11
• Subtask 2: 89 / 89