ll n;
ll ar[300][300];
int main(){
    cin >> n;
    for(ll i = 1; i <= n; i ++) for(ll j = 1; j <= n; j ++) ar[i][j] = 0;
    for(ll i = 1; i <= n; i ++){
        while(1){
            ll x; cin >> x;
            if(x == -1) break;
            ar[x][i] = 1;
        }
    }
    for(ll i = 1; i <= n; i ++) ar[i][n+1] = 1;
    ll col = 1;
    while(col <= n){
        if(ar[col][col] == 1){
            for(ll i = 1; i <= n; i ++){
                if(i == col) continue;
                if(ar[i][col] == 1){
                    //choose ith row
                    for(ll j = 1; j <= n+1; j ++) ar[i][j] = ar[i][j]^ar[col][j];
                }
            }
        }
        else{
            break;
        }
        col ++;
    }
    bool f = 1;
    ll br[300][300];
    for(ll i = 1; i <= n; i ++) for(ll j = 1; j <= n; j ++) if(i==j) br[i][j] = 1;
    for(ll i = 1; i <= n; i ++){
        for(ll j = 1; j <= n; j ++) if(ar[i][j]!=br[i][j]) f = 0;
    }
    if(!f) cout << "No solution" << endl;
    else{
        for(ll i = 1; i <= n; i ++){
            if(ar[i][n+1]==1) cout << i << " ";
        }
    }
    return 0;
}

I have used basic Gauss algorithm making the augmented matrix equal to an identity matrix. Still getting WA. Please help
Thank you :)

Edited by author 04.12.2016 10:11