Submission #103433

#	Time	Username	Problem	Language	Result	Execution time	Memory
103433		wilwxk	Three Friends (BOI14_friends)	C++11	0 / 100	277 ms	263168 KiB

friends

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

const int MAXN=2e6+6;
int cont[MAXN][30], cont2[MAXN][30];
char v[MAXN];
int n;

int main() {
	scanf("%d", &n);
	scanf(" %s", &v[1]);

	for(int i=1; i<=n; i++) {
		for(int j=0; j<=28; j++) cont[i][j]=cont[i-1][j];
			cont[i][v[i]-'A']++;
	}
	for(int i=n; i>=1; i--) {
		for(int j=0; j<=28; j++) cont2[i][j]=cont2[i+1][j];
		cont2[i][v[i]-'A']++;
	}

	int resp=-1;
	for(int i=1; i<=n; i++) {
		bool ok=1;
		for(int j=0; j<=28; j++) {
			if(i<=(n+1)/2) {
				int val=cont[(n+1)/2][j];
				int val2=cont2[(n+1)/2+1][j];
				if(j==v[i]-'A') val--;
				// printf("test %d letra %d > %d %d\n", i, j, val, val2);
				if(val!=val2) { ok=0; break; }
			}
			else {
				int val=cont[n/2][j];
				int val2=cont2[(n+1)/2][j];
				if(j==v[i]-'A') val2--;
				if(val!=val2) { ok=0; break; }
			}
		}
		if(ok) {
			// printf("ok %d\n", i);
			if(resp!=-1) {
				printf("NOT UNIQUE\n");
				return 0;
			}
			resp=i;
		}
	}

	if(resp==-1) {
		printf("NOT POSSIBLE\n");
	}
	else {
		if(resp<=(n+1)/2) {
			for(int i=1; i<=(n+1)/2; i++) {
				if(i==resp) continue;
				printf("%c", v[i]);
			} 
		}
		else {
			for(int i=1; i<=n/2; i++) {
				printf("%c", v[i]);
			}
		}
	}

}

Compilation message (stderr)

friends.cpp: In function 'int main()':
friends.cpp:10:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &n);
  ~~~~~^~~~~~~~~~
friends.cpp:11:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf(" %s", &v[1]);
  ~~~~~^~~~~~~~~~~~~~

• Subtask 1: 0 / 35
• Subtask 2: 0 / 65