Submission #733314

#	Time	Username	Problem	Language	Result	Execution time	Memory
733314		Trunkty	Three Friends (BOI14_friends)	C++14	100 / 100	29 ms	11248 KiB

friends

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

int n;
string u,a,b;
bool pre[2000005],suf[2000005];
bool isa, isb;

signed main(){
	ios::sync_with_stdio(false);
	cin.tie(NULL);
	cin >> n >> u;
	if(n%2==0){
		cout << "NOT POSSIBLE" << "\n";
		return 0;
	}
	n /= 2;
	for(int i=0;i<n;i++){
		a += u[i];
	}
	for(int i=n+1;i<n*2+1;i++){
		b += u[i];
	}
	if(a==b){
		cout << a << "\n";
		return 0;
	}
	for(int i=0;i<n;i++){
		if(i==0){
			if(u[i]==b[i]){
				pre[i] = true;
			}
			else{
				pre[i] = false;
			}
		}
		else{
			if(u[i]==b[i] and pre[i-1]){
				pre[i] = true;
			}
			else{
				pre[i] = false;
			}
		}
	}
	for(int i=n;i>0;i--){
		if(i==n){
			if(u[i]==b[i-1]){
				suf[i] = true;
			}
			else{
				suf[i] = false;
			}
		}
		else{
			if(u[i]==b[i-1] and suf[i+1]){
				suf[i] = true;
			}
			else{
				suf[i] = false;
			}
		}
	}
	if(pre[n-1] or suf[1]){
		isa = true;
	}
	else{
		for(int i=0;i<n-1;i++){
			if(pre[i] and suf[i+2]){
				isa = true;
				break;
			}
		}
	}
	for(int i=n;i<2*n;i++){
		if(i==n){
			if(u[i]==a[i-n]){
				pre[i] = true;
			}
			else{
				pre[i] = false;
			}
		}
		else{
			if(u[i]==a[i-n] and pre[i-1]){
				pre[i] = true;
			}
			else{
				pre[i] = false;
			}
		}
	}
	for(int i=2*n;i>n;i--){
		if(i==2*n){
			if(u[i]==a[i-n-1]){
				suf[i] = true;
			}
			else{
				suf[i] = false;
			}
		}
		else{
			if(u[i]==a[i-n-1] and suf[i+1]){
				suf[i] = true;
			}
			else{
				suf[i] = false;
			}
		}
	}
	if(pre[2*n-1] or suf[n+1]){
		isb = true;
	}
	else{
		for(int i=n;i<2*n-1;i++){
			if(pre[i] and suf[i+2]){
				isb = true;
				break;
			}
		}
	}
	if(isa and isb){
		cout << "NOT UNIQUE" << "\n";
	}
	else{
		if(isa){
			cout << b << "\n";
		}
		else if(isb){
			cout << a << "\n";
		}
		else{
			cout << "NOT POSSIBLE" << "\n";
		}
	}
	return 0;
}

• Subtask 1: 35 / 35
• Subtask 2: 65 / 65