Submission #963950

#	Time	Username	Problem	Language	Result	Execution time	Memory
963950		pcc	Alternating Current (BOI18_alternating)	C++17	13 / 100	30 ms	600 KiB

alternating

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

#define ll long long
#define pll pair<ll,ll>
#define pii pair<int,int>
#define fs first
#define sc second
#define tlll tuple<ll,ll,ll>

const int mxn = 16;
int N,M;
pii arr[mxn];
int ans = -1;
vector<int> paths[mxn];
int col[mxn];

bool inside(pii r,int p){
	if(r.fs<=r.sc){
		if(r.fs<=p&&p<=r.sc)return true;
		else return false;
	}
	else{
		if(p<=r.fs||p>=r.sc)return true;
		else return false;
	}
}

bool banana(int a,int b){
	pii ta = arr[a],tb = arr[b];
	if(inside(ta,tb.fs)||inside(ta,tb.sc)||inside(tb,ta.fs)||inside(tb,ta.sc))return true;
	else return false;
}

void dfs(int now,int c = 1){
	col[now] = c;
	for(auto nxt:paths[now]){
		if(col[nxt]&&col[nxt] != -c){
			cout<<"impossible\n";
			exit(0);
		}
		if(!col[nxt])dfs(nxt,-c);
	}
	return;
}

vector<int> peko[mxn];
int main(){
	ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
	cin>>N>>M;
	for(int i = 0;i<M;i++){
		cin>>arr[i].fs>>arr[i].sc;
		arr[i].fs--,arr[i].sc--;
		int k = arr[i].fs;
		while(k != arr[i].sc){
			peko[k].push_back(i);
			k = (k+1)%N;
		}
		peko[k].push_back(i);
	}
	for(int i = 0;i<N;i++){
		if(peko[i].size() == 2){
			int a = peko[i][0],b = peko[i][1];
			paths[a].push_back(b);
			paths[b].push_back(a);
		}
		if(peko[i].size() < 2){
			cout<<"impossible\n";
			return 0;
		}
	}
	for(int i = 0;i<M;i++){
		if(!col[i])dfs(i);
	}
	for(int i = 0;i<(1<<M);i++){
		int dp[mxn] = {};
		for(int j = 0;j<M;j++){
			int k;
			for(k = arr[j].fs;k != arr[j].sc;k = (k+1)%N){
				dp[k] |= 1<<(i&(1<<j)?1:0);
			}
			dp[k] |= 1<<(i&(1<<j)?1:0);
		}
		if(*min_element(dp,dp+N) == 3)ans = i;
	}
	if(ans == -1)assert(false);
	else{
		for(int i = 0;i<M;i++){
			if(ans&(1<<i))cout<<1;
			else cout<<0;
		}
	}
	return 0;
}

• Subtask 1: 13 / 13
• Subtask 2: 0 / 20
• Subtask 3: 0 / 22
• Subtask 4: 0 / 19
• Subtask 5: 0 / 26