typedef struct CELL {
	int depth;       //  <0 = wall, 0 = unvisited, >0 = visited
	struct CELL *parent;
	struct CELL *next;
} CELL;

CELL cells[4096];

BOOL flood(CELL *_cStart, CELL *_cEnd) {
	int cellOffsets[4] = {1, 64, -1, -64};
	
	CELL *_cListFirst = _cEnd; // candidate list
	CELL *_cListLast = _cEnd;  // at the beginning it only contains the ending point
	_cEnd->depth = 1;          // starting depth
	_cEnd->next = NULL;        // clean the linker
	_cEnd->parent = NULL;      // clean the parent
	
	while(_cListFirst != NULL) {
		CELL *_c = _cListFirst; // take the first member of the candidates list
		_cListFirst = _c->next; // remove it from the list
		int _newDepth = _c->depth + 1;
		int *_off = cellOffsets;
		int *_offLast = _off + 4;
		for(; _off<_offLast; _off+=1) { // 4 directions loop
			CELL *_cT = _c + *_off; // get the neighbor
			if(_cT->depth != 0) // it is a wall or already visited
			   continue;
			_cT->depth = _newDepth;     // set the depth
			_cT->parent = _c;           // set the parent
			_cT->next = NULL;           // clean the linker
			if (_cT == _cStart)         // end when the starting point is reached
				return TRUE;
			
			// include into the candidates list 
			if(!_cListFirst) { // if there are no candidates in the list
				_cListFirst = _cT;
				_cListLast = _cT;
			} else { // otherway, set as the last member in the list
				_cListLast->next = _cT;
				_cListLast = _cT;
			}
		}
	}
	return FALSE;
}