Submission #212297

#	Time	Username	Problem	Language	Result	Execution time	Memory
212297		arnold518	Building 4 (JOI20_building4)	C++14	100 / 100	453 ms	29048 KiB

building4

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

typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

const int MAXN = 1e6;

int N, A[MAXN+10], B[MAXN+10];
int dpl[MAXN+10][2], dpr[MAXN+10][2];

int main()
{
	int i, j, k;

	scanf("%d", &N);
	for(i=1; i<=N*2; i++) scanf("%d", &A[i]);
	for(i=1; i<=N*2; i++) scanf("%d", &B[i]);

	dpl[1][0]=dpr[1][0]=1;
	dpl[1][1]=dpr[1][1]=0;
	for(i=2; i<=N*2; i++)
	{
		dpl[i][0]=dpl[i][1]=987654321;
		dpr[i][0]=dpr[i][1]=-1;
		if(A[i-1]<=A[i])
		{
			dpl[i][0]=min(dpl[i][0], dpl[i-1][0]+1);
			dpr[i][0]=max(dpr[i][0], dpr[i-1][0]+1);
		}
		if(B[i-1]<=A[i])
		{
			dpl[i][0]=min(dpl[i][0], dpl[i-1][1]+1);
			dpr[i][0]=max(dpr[i][0], dpr[i-1][1]+1);	
		}
		if(A[i-1]<=B[i])
		{
			dpl[i][1]=min(dpl[i][1], dpl[i-1][0]);
			dpr[i][1]=max(dpr[i][1], dpr[i-1][0]);
		}
		if(B[i-1]<=B[i])
		{
			dpl[i][1]=min(dpl[i][1], dpl[i-1][1]);
			dpr[i][1]=max(dpr[i][1], dpr[i-1][1]);	
		}
	}

	int p, q=N;

	if(dpl[2*N][0]<=N && N<=dpr[2*N][0]) p=0;
	else if(dpl[2*N][1]<=N && N<=dpr[2*N][1]) p=1;
	else return !printf("-1\n");

	vector<int> ans;
	for(i=2*N; i>=1; i--)
	{
		ans.push_back(p);
		if(p==0)
		{
			q--;
			if(A[i-1]<=A[i] && dpl[i-1][0]<=q && q<=dpr[i-1][0]) p=0;
			if(B[i-1]<=A[i] && dpl[i-1][1]<=q && q<=dpr[i-1][1]) p=1;
		}
		else
		{
			if(A[i-1]<=B[i] && dpl[i-1][0]<=q && q<=dpr[i-1][0]) p=0;
			if(B[i-1]<=B[i] && dpl[i-1][1]<=q && q<=dpr[i-1][1]) p=1;
		}
	}
	reverse(ans.begin(), ans.end());
	for(auto it : ans) printf("%c", it ? 'B' : 'A');
	printf("\n");
}

Compilation message (stderr)

building4.cpp: In function 'int main()':
building4.cpp:15:9: warning: unused variable 'j' [-Wunused-variable]
  int i, j, k;
         ^
building4.cpp:15:12: warning: unused variable 'k' [-Wunused-variable]
  int i, j, k;
            ^
building4.cpp:17:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &N);
  ~~~~~^~~~~~~~~~
building4.cpp:18:29: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  for(i=1; i<=N*2; i++) scanf("%d", &A[i]);
                        ~~~~~^~~~~~~~~~~~~
building4.cpp:19:29: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  for(i=1; i<=N*2; i++) scanf("%d", &B[i]);
                        ~~~~~^~~~~~~~~~~~~

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