Submission #156709

#	Time	Username	Problem	Language	Result	Execution time	Memory
156709		junodeveloper	Three Friends (BOI14_friends)	C++14	100 / 100	56 ms	12004 KiB

friends

#include <bits/stdc++.h>
#define sz(x) ((int)x.size())
#define all(x) (x).begin(), (x).end()
#define fi first
#define se second
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
int n;
char s[2000010];
bool multi;
string solve() {
	string ret="";
	int i,j=-1,cnt=0; bool chk=true;
	for(i=0;i<=n/2;i++) {
		cnt+=s[i]==s[i+n/2];
	}
	for(i=0;i<=n/2;i++) {
		cnt-=s[i]==s[i+n/2];
		if(cnt==n/2) {
			if(j!=-1) {
				//s[j]==s[j+1],s[j+1]==s[j+2],...,s[i-1]==s[i]
				if(!chk) {
					multi=true;
					break;
				}
			}
			j=i;
			chk=true;
		}
		cnt+=s[i]==s[i+n/2+1];
		chk&=s[i]==s[i+1];
	}
	if(j==-1) return ret;
	for(i=0;i<n;i++) {
		if(i==j)continue;
		ret+=s[i];
	}
	ret.erase(ret.begin()+n/2,ret.end());
	return ret;
}
int main() {
	scanf("%d%s",&n,s);
	if(n%2==0){
		puts("NOT POSSIBLE");
		return 0;
	}
	int i;
	string a=solve();
	if(multi) {
		puts("NOT UNIQUE");
		return 0;
	}
	for(i=0;i<n/2;i++) swap(s[i],s[n-i-1]);
	string b=solve();
	if(multi) {
		puts("NOT UNIQUE");
		return 0;
	}
	reverse(b.begin(),b.end());
	if(a.empty() && b.empty()) {
		puts("NOT POSSIBLE");
	} else if(a.empty()) {
		printf("%s",b.c_str());
	} else if(b.empty()) {
		printf("%s", a.c_str());
	} else {
		if(a==b) printf("%s",a.c_str());
		else puts("NOT UNIQUE");
	}
	return 0;
}

Compilation message (stderr)

friends.cpp: In function 'int main()':
friends.cpp:45:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%s",&n,s);
  ~~~~~^~~~~~~~~~~~~

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