Task: Nonoblock
C: #include <stdio.h>
#include <string.h>

void nb(int cells, int total_block_size, int* blocks, int block_count,
        char* output, int offset, int* count) {
    if (block_count == 0) {
        printf("%2d  %s\n", ++*count, output);
        return;
    }
    int block_size = blocks[0];
    int max_pos = cells - (total_block_size + block_count - 1);
    total_block_size -= block_size;
    cells -= block_size + 1;
    ++blocks;
    --block_count;
    for (int i = 0; i <= max_pos; ++i, --cells) {
        memset(output + offset, '.', max_pos + block_size);
        memset(output + offset + i, '#', block_size);
        nb(cells, total_block_size, blocks, block_count, output,
           offset + block_size + i + 1, count);
    }
}

void nonoblock(int cells, int* blocks, int block_count) {
    printf("%d cells and blocks [", cells);
    for (int i = 0; i < block_count; ++i)
        printf(i == 0 ? "%d" : ", %d", blocks[i]);
    printf("]:\n");
    int total_block_size = 0;
    for (int i = 0; i < block_count; ++i)
        total_block_size += blocks[i];
    if (cells < total_block_size + block_count - 1) {
        printf("no solution\n");
        return;
    }
    char output[cells + 1];
    memset(output, '.', cells);
    output[cells] = '\0';
    int count = 0;
    nb(cells, total_block_size, blocks, block_count, output, 0, &count);
}

int main() {
    int blocks1[] = {2, 1};
    nonoblock(5, blocks1, 2);
    printf("\n");
    
    nonoblock(5, NULL, 0);
    printf("\n");

    int blocks2[] = {8};
    nonoblock(10, blocks2, 1);
    printf("\n");
    
    int blocks3[] = {2, 3, 2, 3};
    nonoblock(15, blocks3, 4);
    printf("\n");
    
    int blocks4[] = {2, 3};
    nonoblock(5, blocks4, 2);

    return 0;
}

Python: def nonoblocks(blocks, cells):
    if not blocks or blocks[0] == 0:
        yield [(0, 0)]
    else:
        assert sum(blocks) + len(blocks)-1 <= cells, \
            'Those blocks will not fit in those cells'
        blength, brest = blocks[0], blocks[1:]      
        minspace4rest = sum(1+b for b in brest)     
        
        for bpos in range(0, cells - minspace4rest - blength + 1):
            if not brest:
                
                yield [(bpos, blength)]
            else:
                
                
                
                offset = bpos + blength +1
                nonoargs = (brest, cells - offset)  
                
                for subpos in nonoblocks(*nonoargs):
                    
                    rest = [(offset + bp, bl) for bp, bl in subpos]
                    
                    vec = [(bpos, blength)] + rest
                    yield vec

def pblock(vec, cells):
    'Prettyprints each run of blocks with a different letter A.. for each block of filled cells'
    vector = ['_'] * cells
    for ch, (bp, bl) in enumerate(vec, ord('A')):
        for i in range(bp, bp + bl):
            vector[i] = chr(ch) if vector[i] == '_' else'?'
    return '|' + '|'.join(vector) + '|'


if __name__ == '__main__':
    for blocks, cells in (
            ([2, 1], 5),
            ([], 5),
            ([8], 10),
            ([2, 3, 2, 3], 15),
           
           
           
            ([2, 3], 5),
            ):
        print('\nConfiguration:\n    %s 
        print('  Possibilities:')
        for i, vector in enumerate(nonoblocks(blocks, cells)):
            print('   ', pblock(vector, cells))
        print('  A total of %i Possible configurations.' % (i+1))