Task: Nonoblock
C#: using System;
using System.Linq;
using System.Text;

public static class Nonoblock
{
    public static void Main() {
        Positions(5, 2,1);
        Positions(5);
        Positions(10, 8);
        Positions(15, 2,3,2,3);
        Positions(5, 2,3);
    }

    public static void Positions(int cells, params int[] blocks) {
        if (cells < 0 || blocks == null || blocks.Any(b => b < 1)) throw new ArgumentOutOfRangeException();
        Console.WriteLine($"{cells} cells with [{string.Join(", ", blocks)}]");
        if (blocks.Sum() + blocks.Length - 1 > cells) {
            Console.WriteLine("No solution");
            return;
        }
        var spaces = new int[blocks.Length + 1];
        int total = -1;
        for (int i = 0; i < blocks.Length; i++) {
            total += blocks[i] + 1;
            spaces[i+1] = total;
        }
        spaces[spaces.Length - 1] = cells - 1;
        var sb = new StringBuilder(string.Join(".", blocks.Select(b => new string('#', b))).PadRight(cells, '.'));
        Iterate(sb, spaces, spaces.Length - 1, 0);
        Console.WriteLine();
    }

    private static void Iterate(StringBuilder output, int[] spaces, int index, int offset) {
        Console.WriteLine(output.ToString());
        if (index <= 0) return;
        int count = 0;
        while (output[spaces[index] - offset] != '#') {
            count++;
            output.Remove(spaces[index], 1);
            output.Insert(spaces[index-1], '.');
            spaces[index-1]++;
            Iterate(output, spaces, index - 1, 1);
        }
        if (offset == 0) return;
        spaces[index-1] -= count;
        output.Remove(spaces[index-1], count);
        output.Insert(spaces[index] - count, ".", count);
    }

}

C++: #include <iomanip>
#include <iostream>
#include <algorithm>
#include <numeric>
#include <string>
#include <vector>

typedef std::pair<int, std::vector<int> > puzzle;

class nonoblock {
public:
    void solve( std::vector<puzzle>& p ) {
        for( std::vector<puzzle>::iterator i = p.begin(); i != p.end(); i++ ) {
            counter = 0;
            std::cout << " Puzzle: " << ( *i ).first << " cells and blocks [ ";
            for( std::vector<int>::iterator it = ( *i ).second.begin(); it != ( *i ).second.end(); it++ )
                std::cout << *it << " ";
            std::cout << "] ";
            int s = std::accumulate( ( *i ).second.begin(), ( *i ).second.end(), 0 ) + ( ( *i ).second.size() > 0 ? ( *i ).second.size() - 1 : 0 );
            if( ( *i ).first - s < 0 ) {
                std::cout << "has no solution!\n\n\n";
                continue;
            }
            std::cout << "\n Possible configurations:\n\n";
            std::string b( ( *i ).first, '-' );
            solve( *i, b, 0 );
            std::cout << "\n\n";
        } 
    }

private:
    void solve( puzzle p, std::string n, int start ) {
        if( p.second.size() < 1 ) {
            output( n );
            return;
        }
        std::string temp_string;
        int offset,
            this_block_size = p.second[0];

        int space_need_for_others = std::accumulate( p.second.begin() + 1, p.second.end(), 0 );
        space_need_for_others += p.second.size() - 1;

        int space_for_curr_block = p.first - space_need_for_others - std::accumulate( p.second.begin(), p.second.begin(), 0 );

        std::vector<int> v1( p.second.size() - 1 );
        std::copy( p.second.begin() + 1, p.second.end(), v1.begin() );
        puzzle p1 = std::make_pair( space_need_for_others, v1 );

        for( int a = 0; a < space_for_curr_block; a++ ) {
            temp_string = n;

            if( start + this_block_size > n.length() ) return;

            for( offset = start; offset < start + this_block_size; offset++ )
                temp_string.at( offset ) = 'o';

            if( p1.first ) solve( p1, temp_string, offset + 1 );
            else output( temp_string );

            start++;
        }
    }
    void output( std::string s ) {
        char b = 65 - ( s.at( 0 ) == '-' ? 1 : 0 );
        bool f = false;
        std::cout << std::setw( 3 ) << ++counter << "\t|";
        for( std::string::iterator i = s.begin(); i != s.end(); i++ ) {
            b += ( *i ) == 'o' && f ? 1 : 0;
            std::cout << ( ( *i ) == 'o' ? b : '_' ) << "|";
            f = ( *i ) == '-' ? true : false;
        }
        std::cout << "\n";
    }

    unsigned counter;
};

int main( int argc, char* argv[] )
{
    std::vector<puzzle> problems;
    std::vector<int> blocks; 
    blocks.push_back( 2 ); blocks.push_back( 1 );
    problems.push_back( std::make_pair( 5, blocks ) );
    blocks.clear();
    problems.push_back( std::make_pair( 5, blocks ) );
    blocks.push_back( 8 );
    problems.push_back( std::make_pair( 10, blocks ) );
    blocks.clear();
    blocks.push_back( 2 ); blocks.push_back( 3 );
    problems.push_back( std::make_pair( 5, blocks ) );
    blocks.push_back( 2 ); blocks.push_back( 3 );
    problems.push_back( std::make_pair( 15, blocks ) );

    nonoblock nn;
    nn.solve( problems );

    return 0;
}