第23回オフラインリアルタイムどう書く を C++ で解く

#include <iostream>
#include <sstream>
#include <string>
#include <algorithm>

struct Cell
{
    int value;
    int length;

    Cell() : value(0), length(0) {}
};

int get_length(Cell table[5][5], int row, int col)
{
    if(table[row][col].length == 0)
    {
        table[row][col].length = 1;

        if((row > 0) && (table[row][col].value < table[row - 1][col].value))
        {
            table[row][col].length = std::max(get_length(table, row - 1, col) + 1, table[row][col].length);
        }

        if((row < 4) && (table[row][col].value < table[row + 1][col].value))
        {
            table[row][col].length = std::max(get_length(table, row + 1, col) + 1, table[row][col].length);
        }

        if((col > 0) && (table[row][col].value < table[row][col - 1].value))
        {
            table[row][col].length = std::max(get_length(table, row, col - 1) + 1, table[row][col].length);
        }

        if((col < 4) && (table[row][col].value < table[row][col + 1].value))
        {
            table[row][col].length = std::max(get_length(table, row, col + 1) + 1, table[row][col].length);
        }
    }

    return table[row][col].length;
}

std::string solve(const std::string& input)
{
    Cell table[5][5];
    for(int row = 0; row < 5; ++row)
    {
        for(int col = 0; col < 5; ++col)
        {
            table[row][col].value = input[row * 6 + col] - '0';
        }
    }

    int length = 0;
    for(int row = 0; row < 5; ++row)
    {
        for(int col = 0; col < 5; ++col)
        {
            length = std::max(get_length(table, row, col), length);
        }
    }

    std::ostringstream oss;
    oss << length;

    return oss.str();
}

void test(const std::string& input, const std::string& expected)
{
    std::string actual = solve(input);
    if(expected == actual)
    {
        std::cout << "." << std::flush;
    }
    else
    {
        std::cout << "\ninput: " << input << ", expected: " << expected << ", acutal: " << actual << std::endl;
    }
}

int main(int argc, char* argv[])
{
    /*0*/ test( "01224/82925/69076/32298/21065", "6" );
    /*1*/ test( "03478/12569/03478/12569/03478", "10" );
    /*2*/ test( "09900/28127/87036/76545/87650", "10" );
    /*3*/ test( "77777/77777/77777/77777/77777", "1" );
    /* ... */
    /*50*/ test( "02489/77571/84873/03879/84460", "7" );

    std::cout << std::endl;

    return 0;
}