НП Лаб6 Зад1

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.*;

public class Has3sumTest {
    public static void main(String[] args) throws IOException {
        BufferedReader jin = new BufferedReader(
                new InputStreamReader(System.in));
        int n = Integer.parseInt(jin.readLine());
        String nums[] = jin.readLine().split("\\s+");
        int a[] = new int[n];
        for (int i = 0; i < n; ++i)
            a[i] = Integer.parseInt(nums[i]);
        System.out.println(has3sum(a));
    }

    public static boolean has3sum(int a[]) {
        if(a.length<3) return false;
        Set<Integer> set1 = new HashSet<Integer>();
        for(int i=0;i<a.length;i++){
            set1.add(a[i]);
        }
        Iterator<Integer> set1it = set1.iterator();
        Iterator<Integer> set2it = set1.iterator();
        set2it.next();
        while(set1it.hasNext()){
            int br1 = set1it.next();
            while(set2it.hasNext()){
                int br2 = set2it.next();
                if(set1.contains(-br1-br2)){
                    return true;
                }
            }
            set2it = set1.iterator();
        }

        return false;
    }

    public static boolean has3sumtree(int a[]) {
        if(a.length<3) return false;
        Set<Integer> set1 = new TreeSet<Integer>();
        for(int i=0;i<a.length;i++){
            set1.add(a[i]);
        }
        Iterator<Integer> set1it = set1.iterator();
        Iterator<Integer> set2it = set1.iterator();
        set2it.next();
        while(set1it.hasNext()){
            int br1 = set1it.next();
            while(set2it.hasNext()){
                int br2 = set2it.next();
                if(set1.contains(-br1-br2)){
                    return true;
                }
            }
            set2it = set1.iterator();
        }

        return false;
    }
}