Submission #41125

#	Time	Username	Problem	Language	Result	Execution time	Memory
41125		14kg	Three Friends (BOI14_friends)	C++11	100 / 100	75 ms	19636 KiB

friends

#include <stdio.h>
#define N 2000005

int n, link[N];
char in[N];

int main(){
    int scnt=0, out=0, len=0;
    scanf("%d %s",&n,in+1);

    if(n%2==0){ printf("NOT POSSIBLE"); return 0; }
    for(int i=2; i<=n/2+1; i++){
        int j=n/2+i;
        scnt+=(in[i]==in[j]);
        link[i]=j, link[j]=i;
    }

    if(scnt==n/2) out=1;
    for(int i=2; i<=n; i++){
        int x=i-1, y=link[i];

        scnt-=(in[i]==in[y]);
        link[x]=y, link[y]=x;
        scnt+=(in[x]==in[y]);

        if(scnt==n/2 && out){
            if(out==i-1 && in[i-1]==in[i]) out++;
            else{ printf("NOT UNIQUE"); return 0; }
        }
        else if(scnt==n/2) out=i;
    }

    if(!out){ printf("NOT POSSIBLE"); return 0; }
    for(int i=1; len<n/2; i++){
        if(i==out) continue;
        len++, printf("%c",in[i]);
    }
}

Compilation message (stderr)

friends.cpp: In function 'int main()':
friends.cpp:9:27: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d %s",&n,in+1);
                           ^

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