Submission #657157

#	Time	Username	Problem	Language	Result	Execution time	Memory
657157		Juan	Three Friends (BOI14_friends)	C++17	100 / 100	128 ms	7488 KiB

friends

#include<bits/stdc++.h>
using namespace std;
const int maxn = 2e6 + 5;

char v[maxn];

int main(){
	int n; cin >> n;
	for(int i = 0; i < n; i++) cin >> v[i];

	int ok = 0, diffcnt = 0;
	string ans = "", left="", right="";
	for(int i = 0; i < n/2; i++) left+=v[i];
	for(int i = n/2; i < n-1; i++) right+=v[i];
	for(int i = 0; i < n/2; i++) if(left[i]!=right[i]) diffcnt++;
	if(!diffcnt) ok++, ans = right;

	for(int i = n-2; i >= n/2; i--){
		int op;
		if(right[i-n/2] == left[i-n/2]) op=-1; else op = -2;
		right[i-n/2] = v[i+1];
		if(right[i-n/2] == left[i-n/2]) op+=1; else op += 2;
		diffcnt+=op;
		if(!diffcnt){
			ok++;
			if(ok>=2 && op) {cout << "NOT UNIQUE\n"; return 0;}
			if(ok==1) ans=right;
		}
	}
	for(int i = n/2-1; i >= 0; i--){
		int op;
		if(left[i] == right[i]) op=-1; else op = -2;
		left[i] = v[i+1];
		if(left[i] == right[i]) op+=1; else op += 2;
		diffcnt+=op;
		if(!diffcnt){
			ok++;
			if(ok>=2 && op) {cout << "NOT UNIQUE\n"; return 0;}
			if(ok==1) ans=left;
		}
	}

	if(ok==0) cout << "NOT POSSIBLE\n";
	else cout << ans << '\n';
}

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