/*
VIM: let b:lcppflags="-std=c++14 -O2 -pthread"
VIM: let b:wcppflags="/O2 /EHsc /DWIN32"
VIM-: let b:argv=""
*/
#include <iostream>
#include <exception>
#include <vector>
#include <string>
#include <unordered_map>

/*
 FB On-site March 

    Q: Find number of Islands. 
    XXXOO 
    OOOXX 
    XXOOX 
    Return 3 islands. 
    1 1 1 O O
    O O O 2 2
    3 3 O O 2
*/
int number_of_islands( const std::vector<std::string>& board )
{
    auto n = board.size();
    auto m = board.front().size();
    std::unordered_map<int,int> g;

    auto idx = [m](size_t i, size_t j){
        return i*m+j;
    };

    auto root = [&g](size_t idx){
        for (; g[idx] != idx; idx = g[idx] );
        return idx;
    };

    for (size_t i = 0; i < n; ++i ){
        for (size_t j = 0; j < m; ++j){
            if (board[i][j] == 'x'){
                if (j>0 && board[i][j-1] == 'x'){
                    g[idx(i,j)]=g[idx(i,j-1)];
                    if (i>0 && board[i-1][j] == 'x'){
                        g[root(idx(i-1,j))]=g[idx(i,j)];
                    }
                }
                else if (i>0 && board[i-1][j] == 'x'){
                    g[idx(i,j)]=g[idx(i-1,j)];
                }
                else {
                    g[idx(i,j)]=idx(i,j);
                }
            }
        }
    }

    int count = 0;
    for ( const auto& node: g){
        if ( node.first == node.second ){
            ++count;
        }
    }

    return count;
}

int main ( void )
{try{

    std::cout << number_of_islands({
                "xxxoo",
                "oooxx",
                "xxoox"
            }) << std::endl;

    std::cout << number_of_islands({
                ".xx..",
                "xx...",
                "xxxxx"
            }) << std::endl;
    std::cout << number_of_islands({
                "....x",
                "....x",
                "xxxxx"
            }) << std::endl;
    std::cout << number_of_islands({
                "xxxxx",
                "xxxxx",
                "xxxxx"
            }) << std::endl;
    std::cout << number_of_islands({
                "xxxxx",
                "....x",
                "xxx.x",
                "x...x",
                "xxxxx"
            }) << std::endl;


    return 0;
}
catch ( const std::exception& e )
{
    std::cerr << std::endl
            << "std::exception(\"" << e.what() << "\")." << std::endl;
    return 2;
}
catch ( ... )
{
    std::cerr  << std::endl
            << "unknown exception." << std::endl;
    return 1;
}}