from typing import Optional, List, Dict, Set

class Heap:
    def __init__( self ) -> None:
        self.fro : List[ List[ int ] ] = []
        self.to  : List[ List[ int ] ] = []
        self.scan = 0

    def boundcheck( self, obj_id: int, index: int ) -> bool:
        return obj_id >= 0 and \
               obj_id < len( self.to ) and \
               index < len( self.to[ obj_id ] )

    def read( self, obj_id: int, index: int ) -> Optional[int]:
        if not self.boundcheck( obj_id, index ):
            return None
        return self.to[ obj_id ][ index ]

    def write( self, obj_id: int, index: int, value: int ) -> bool:
        if not self.boundcheck( obj_id, index ):
            return False
        self.to[ obj_id ][ index ] = value
        return True

    def collect( self ) -> None:
        self.fro = self.to
        self.to = []

        self.scan = 0
        assert self.copy( 0 ) == 0

        while self.scan < len( self.to ):
            o = self.to[ self.scan ]
            for i in range( len( o ) ):
                o[ i ] = self.copy( o[ i ] )
            self.scan += 1

        print( self.to )

    def copy( self, ref: int ) -> int:
        if ref < 0:
            return ref

        nref = self.fro[ ref ][ 0 ] - len( self.fro )

        if nref < 0:
            nref = len( self.to )
            self.to.append( self.fro[ ref ].copy() )
            self.fro[ ref ][ 0 ] = nref + len( self.fro )

        return nref

    def make( self, size: int ) -> int:
        self.to.append( [ 0 for _ in range( size ) ] )
        return len( self.to ) - 1

import run_tests