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 C++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <bits/stdc++.h>
using namespace std;
vector<int> visited;
vector<vector<int> > vec;
int dfs(int x){
  visited[x]=true;
  int cnt = 0;
  for(int i = 0; i < vec[x].size(); ++i){
    if(!visited[vec[x][i]]){
      cnt = dfs(vec[x][i]) + 1;
    }
  }
  return cnt;
}

int main(){
  int n, a, x, y;
  cin>>n;
  vec.resize(n);
  for(int j = 0; j < n; ++j){
    cin>>a;
    for(int i = 0; i < a; ++i){
      cin>>x>>y;
      x--;
      if(y)vec[x].push_back(i);
      else vec[i].push_back(x);
    }
  }
  for(int i = 0; i < n; ++i){
    visited.clear();
    visited.resize(n, false);
    cout<<dfs(i)<<endl;
  }
  return 0;
}