Problem:
Score : 300 points

Problem Statement

There are N people numbered 1 to N. Each of them is either an honest person whose testimonies are always correct or an unkind person whose testimonies may be correct or not.

Person i gives A_i testimonies. The j-th testimony by Person i is represented by two integers x_{ij} and y_{ij}. If y_{ij} = 1, the testimony says Person x_{ij} is honest; if y_{ij} = 0, it says Person x_{ij} is unkind.

How many honest persons can be among those N people at most?

Constraints

All values in input are integers.

1 \leq N \leq 15

0 \leq A_i \leq N - 1

1 \leq x_{ij} \leq N

x_{ij} \neq i

x_{ij_1} \neq x_{ij_2} (j_1 \neq j_2)

y_{ij} = 0, 1

Input

Input is given from Standard Input in the following format:

N
A_1
x_{11} y_{11}
x_{12} y_{12}
:
x_{1A_1} y_{1A_1}
A_2
x_{21} y_{21}
x_{22} y_{22}
:
x_{2A_2} y_{2A_2}
:
A_N
x_{N1} y_{N1}
x_{N2} y_{N2}
:
x_{NA_N} y_{NA_N}

Output

Print the maximum possible number of honest persons among the N people.

Sample Input 1

3
1
2 1
1
1 1
1
2 0

Sample Output 1

2

If Person 1 and Person 2 are honest and Person 3 is unkind, we have two honest persons without inconsistencies, which is the maximum possible number of honest persons.

Sample Input 2

3
2
2 1
3 0
2
3 1
1 0
2
1 1
2 0

Sample Output 2

0

Assuming that one or more of them are honest immediately leads to a contradiction.

Sample Input 3

2
1
2 0
1
1 0

Sample Output 3

1

Solution in Java (OpenJDK 11.0.6) (judge verdict: Accepted)

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int max = 1;
		for(int i=0;i<N;i++) {
			max *=2;
		}
		max--;
		List<List<People>> list = new ArrayList<List<People>>();
		Main main = new Main ();
		for(int i=0;i<N;i++) {
			int q = sc.nextInt();
			List<People> l = new ArrayList<People>();
			for (int j=0;j<q;j++) {
				People p = main.new People();
				p.p = sc.nextInt();
				p.b = sc.nextInt();
				l.add(p);
			}
			list.add(l);
		}
		int re = 0;
		while (max>0) {
			int a[] = new int[N];
			int i=0;
			int t = max;
			int count =0;
			while (t>0) {
				if (t%2==1) {
					a[i]++;
					count ++;
				}
				t = t/2;
				i++;
			}
			boolean b =true;
			for(int j=0;j<N;j++) {
				if (a[j]==1) {
					List<People> l = list.get(j);
					for (int k =0;k<l.size();k++) {
						if (l.get(k).b!=a[l.get(k).p-1]) {
							b = false;
							break;
						}
					}
					if (b==false) {
						break;
					}
				}
			}
			if (b) {
				if (count>re) {
					re = count;
				}
			}
			max--;
		}
		System.out.println(re);
	}
	public class People {
		int p;
		int b;

	}
}