c++ - 2-3-4 泄漏的析构函数

Question

如果我没记错的话，当涉及到2-3-4 树 的破坏时，它应该类似于二叉树，只有 4 个 child (递归)。下面是我的特定于析构函数的代码，带有简单的递归删除。

问题是我仍然漏水。该文件仅包含我的 2-3-4 树。

我相信这是为 2-3-4 树 实现析构函数的正确方法，但我的实现似乎不正确。谁能指出我的逻辑错误？我画了图表，看起来不错。

//Destructor    
template < typename KEY , typename T >
Map< KEY , T >::~Map(){

    destructCode();
}

//Common code for deallocation
template < typename KEY , typename T >
void Map< KEY , T >::destructCode(){
    destruct( _root );
}

//Recursive delete helper
template < typename KEY , typename T >
void Map< KEY , T >::destruct( Elem* node ){
    if( node -> cOne )
        destruct( node -> cOne );

    if( node -> cTwo )
        destruct( node -> cTwo );

    if( node -> cThree )
        destruct( node -> cThree );

    if( node -> cFour )
        destruct( node -> cFour );

    delete node;
}

我的节点设计:

Elem {
    KEY k1, k2, k3;
    T t1, t2, t3;

    //Children
    Elem *cOne, *cTwo, *cThree, *cFour;

    Elem *parent;

    //numChildren = #node type
    //Contains numChildren - 1 data items
    int _numChildren;
};

我的插入代码。我目前还没有实现删除功能。

//Sorts the keys of the node to include the new keyvalue pairing
template < typename KEY , typename T >
void Map< KEY , T >::keyAdding( KEY k , T t , Elem * node , Elem * smaller , Elem * bigger ){

    if( node -> _numChildren == 4 )//3 keys already
        cout << "Problem; adding a key to a 4-node" << endl;

    else if( node -> _numChildren == 3 ){//2 keys

        if( k < node -> k1 ){//Smallest of the three

            node -> k3 = node -> k2;
            node -> t3 = node -> t2;
            node -> k2 = node -> k1;
            node -> t2 = node -> t1;
            node -> k1 = k;
            node -> t1 = t;

            node -> cFour = node -> cThree;
            node -> cThree = node -> cTwo;
            node -> cTwo = bigger;
            node -> cOne = smaller;         
        }

        else if( k < node -> k2 ){//Mid

            node -> k3 = node -> k2;
            node -> t3 = node -> t2;
            node -> k2 = k;
            node -> t2 = t;

            node -> cFour = node -> cThree;
            node -> cThree = bigger;
            node -> cTwo = smaller;
        }

        else{//Largest

            node -> k3 = k;
            node -> t3 = t;

            node -> cFour = bigger;
            node -> cThree = smaller;
        }
        node -> _numChildren++;
    }

    else{//1 key

        if( k < node -> k1 ){

            node -> k2 = node -> k1;
            node -> t2 = node -> t1;
            node -> k1 = k;
            node -> t1 = t;

            node -> cThree = node -> cTwo;
            node -> cTwo = bigger;
            node -> cOne = smaller;
        }

        else{

            node -> k2 = k;
            node -> t2 = t;

            node -> cThree = bigger;
            node -> cTwo = smaller;
        }
        node -> _numChildren++;
    }   
}


//Sorts the keys of the node to include the new keyvalue pairing
template < typename KEY , typename T >
void Map< KEY , T >::keyAdding( KEY k , T t , Elem * node ){

    if( node -> _numChildren == 4 )//3 keys already
        cout << "Problem; adding a key to a 4-node" << endl;

    else if( node -> _numChildren == 3 ){//2 keys

        if( k < node -> k1 ){//Smallest of the three

            node -> k3 = node -> k2;
            node -> t3 = node -> t2;
            node -> k2 = node -> k1;
            node -> t2 = node -> t1;
            node -> k1 = k;
            node -> t1 = t; 
        }

        else if( k < node -> k2 ){//Mid

            node -> k3 = node -> k2;
            node -> t3 = node -> t2;
            node -> k2 = k;
            node -> t2 = t;
        }

        else{//Largest

            node -> k3 = k;
            node -> t3 = t;
        }
        node -> _numChildren++;
    }

    else{//1 key

        if( k < node -> k1 ){

            node -> k2 = node -> k1;
            node -> t2 = node -> t1;
            node -> k1 = k;
            node -> t1 = t;
        }

        else{

            node -> k2 = k;
            node -> t2 = t;
        }
        node -> _numChildren++;
    }   
}


//Insert, return true if successful.
template < typename KEY , typename T >
bool Map< KEY , T >::insert(KEY k , T t ){

    if( _root == 0 ){//Empty

        _root = new Elem;

        _root -> _numChildren = 2;
        _root -> cOne = NULL;
        _root -> cTwo = NULL;
        _root -> cThree = NULL;
        _root -> cFour = NULL;
        _root -> k1 = k;
        _root -> t1 = t;
        _size++;

        return true;
    }

    else
        return insert( k , t , _root );
}

//Recursive insert helper
template < typename KEY , typename T >
bool Map< KEY , T >::insert(KEY k , T t , Elem * rRoot ){

    Elem * temp = rRoot;

    if( temp -> _numChildren == 4 ){//4-node

        //Save middle value.
        KEY kTemp = temp -> k2;
        T tTemp = temp -> t2;

        //Remove middle value, making a 3-node.
        temp -> k2 = temp -> k3;
        temp -> t2 = temp -> t3;
        //temp -> k3 = NULL;
        //temp -> t3 = NULL;
        temp -> _numChildren--;

        //Split the (now) 3-node into a pair of 2-nodes
        Elem * twoNode1 = new Elem;
        twoNode1 -> _numChildren = 2;
        twoNode1 -> parent = temp -> parent;
        twoNode1 -> cOne = temp -> cOne;
        twoNode1 -> cTwo = temp -> cTwo;
        twoNode1 -> k1 = temp -> k1;
        twoNode1 -> t1 = temp -> t1;

        if( twoNode1 -> cOne )
            twoNode1 -> cOne -> parent = twoNode1;

        if( twoNode1 -> cTwo )
            twoNode1 -> cTwo -> parent = twoNode1;

        //2-nodes do not have values for these.
        twoNode1 -> cThree = NULL;
        twoNode1 -> cFour = NULL;
        //twoNode1 -> k2 = NULL;
        //twoNode1 -> t2 = NULL;
        //twoNode1 -> k3 = NULL;
        //twoNode1 -> t3 = NULL;

        //Second 2-node...
        Elem * twoNode2 = new Elem;
        twoNode2 -> _numChildren = 2;
        twoNode2 -> parent = temp -> parent;
        twoNode2 -> cOne = temp -> cThree;
        twoNode2 -> cTwo = temp -> cFour;
        twoNode2 -> k1 = temp -> k3;
        twoNode2 -> t1 = temp -> t3;

        if( twoNode2 -> cOne )
            twoNode2 -> cOne -> parent = twoNode1;

        if( twoNode2 -> cTwo )
            twoNode2 -> cTwo -> parent = twoNode1;

        //2-Nodes do not have values for these.
        twoNode2 -> cThree = NULL;
        twoNode2 -> cFour = NULL;
        //twoNode2 -> k2 = NULL;
        //twoNode2 -> t2 = NULL;
        //twoNode2 -> k3 = NULL;
        //twoNode2 -> t3 = NULL;

        //We're at the root node.
        if( temp == _root ){

            _root -> _numChildren = 2;
            _root -> parent = NULL; //Root has no parent, silly.
            _root -> cOne = twoNode1;
            _root -> cTwo = twoNode2;
            _root -> k1 = kTemp;
            _root -> t1 = tTemp;

            //2-Nodes do not have values for these.
            _root -> cThree = NULL;
            _root -> cFour = NULL;
            //_root -> k2 = NULL;
            //_root -> t2 = NULL;
            //_root -> k3 = NULL;
            //_root -> t3 = NULL;

            //Update split node's parent
            twoNode1 -> parent = _root;
            twoNode2 -> parent = _root;

            //Height has increased.
            _height++;

            //Ascend to root.
            temp = _root;
        }

        //A generic 4-node somewhere in the tree.
        else{

            Elem * ntemp = temp;
            temp = temp -> parent;

            //Update split node's parent
            twoNode1 -> parent = temp;
            twoNode2 -> parent = temp;

            keyAdding( kTemp , tTemp , temp , twoNode1 , twoNode2 );
        }
    }//4-node end

    //Check if leaf
    if( temp -> cOne == 0 && temp -> cTwo == 0 && temp -> cThree == 0 && temp -> cFour == 0 ){

        keyAdding( k , t , temp );
        _size++;
        return true;
    }

    else{

        if( temp -> _numChildren == 4 ){

            cout << "Should not have a 4-node in leaf-checking.\n";
            return -5;
        }

        else if( temp -> _numChildren == 3 ){

            if( k < temp -> k1 )
                insert( k , t , temp -> cOne );

            else if( k < temp -> k2 )
                insert( k , t , temp -> cTwo );

            else
                insert( k , t , temp -> cThree);
        }

        else{

            if( k < temp -> k1 )
                insert( k , t , temp -> cOne );

            else
                insert( k , t , temp -> cTwo );
        }   
    }
}

---

瓦尔格林德:

-bash-4.2$ valgrind -v ./a.out
==18357== Memcheck, a memory error detector
==18357== Copyright (C) 2002-2010, and GNU GPL'd, by Julian Seward et al.
==18357== Using Valgrind-3.6.1 and LibVEX; rerun with -h for copyright info
==18357== Command: ./a.out
==18357== 
--18357-- Valgrind options:
--18357--    -v
--18357-- Contents of /proc/version:
--18357--   Linux version 3.6.11-1.fc16.i686.PAE (mockbuild@bkernel02) (gcc version 4.6.3 20120306 (Red Hat 4.6.3-2) (GCC) ) #1 SMP Mon Dec 17 21:31:29 UTC 2012
--18357-- Arch and hwcaps: X86, x86-sse1-sse2
--18357-- Page sizes: currently 4096, max supported 4096
--18357-- Valgrind library directory: /usr/lib/valgrind
--18357-- Reading syms from /home/csu/jan99/Documents/CS515/A8/a.out (0x8048000)
--18357-- Reading syms from /usr/lib/valgrind/memcheck-x86-linux (0x38000000)
--18357--    object doesn't have a dynamic symbol table
--18357-- Reading syms from /lib/ld-2.14.90.so (0x463f2000)
--18357--   Considering /usr/lib/debug/.build-id/6f/895b79f95b39ef92d24ff50a16ff774b34b527.debug ..
--18357--   .. build-id is valid
--18357-- Reading suppressions file: /usr/lib/valgrind/default.supp
--18357-- REDIR: 0x4640b610 (strlen) redirected to 0x38052c08 (vgPlain_x86_linux_REDIR_FOR_strlen)
--18357-- REDIR: 0x4640b390 (index) redirected to 0x38052be3 (vgPlain_x86_linux_REDIR_FOR_index)
--18357-- Reading syms from /usr/lib/valgrind/vgpreload_core-x86-linux.so (0x4001000)
--18357-- Reading syms from /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so (0x4004000)
==18357== WARNING: new redirection conflicts with existing -- ignoring it
--18357--     new: 0x4640b390 (index               ) R-> 0x04008270 index
==18357== WARNING: new redirection conflicts with existing -- ignoring it
--18357--     new: 0x4640b610 (strlen              ) R-> 0x040086d0 strlen
--18357-- Reading syms from /usr/lib/libstdc++.so.6.0.16 (0x46971000)
--18357--   Considering /usr/lib/debug/.build-id/19/bce624dda8659f770012166d85bc075fb23f1a.debug ..
--18357--   .. build-id is valid
--18357-- Reading syms from /lib/libm-2.14.90.so (0x465e7000)
--18357--   Considering /usr/lib/debug/.build-id/b8/362b3b5d82f212d77d69fff8e503ae6fdcfe9b.debug ..
--18357--   .. build-id is valid
--18357-- Reading syms from /lib/libgcc_s-4.6.3-20120306.so.1 (0x4663f000)
--18357--   Considering /usr/lib/debug/.build-id/4b/65b2ab36082e9552ad2014fac436421c4f65ad.debug ..
--18357--   .. build-id is valid
--18357-- Reading syms from /lib/libc-2.14.90.so (0x46417000)
--18357--   Considering /usr/lib/debug/.build-id/ea/4850e94d2deab52b8469f1e68a98f4d6229e48.debug ..
--18357--   .. build-id is valid
--18357-- REDIR: 0x46498a40 (__GI_strrchr) redirected to 0x40080d0 (__GI_strrchr)
--18357-- REDIR: 0x46498780 (__GI_strlen) redirected to 0x40086b0 (__GI_strlen)
--18357-- REDIR: 0x46497fb0 (strcmp) redirected to 0x40014c0 (_vgnU_ifunc_wrapper)
--18357-- REDIR: 0x46562db0 (__strcmp_ssse3) redirected to 0x4009250 (strcmp)
--18357-- REDIR: 0x46498730 (strlen) redirected to 0x40014c0 (_vgnU_ifunc_wrapper)
--18357-- REDIR: 0x4649f3e0 (__strlen_sse2_bsf) redirected to 0x4008690 (strlen)
--18357-- REDIR: 0x46a24350 (operator new(unsigned int)) redirected to 0x4007820 (operator new(unsigned int))
--18357-- REDIR: 0x46499fa0 (memcpy) redirected to 0x40014c0 (_vgnU_ifunc_wrapper)
--18357-- REDIR: 0x4655ab70 (__memcpy_ssse3) redirected to 0x4009420 (memcpy)
--18357-- REDIR: 0x464994c0 (bcmp) redirected to 0x40014c0 (_vgnU_ifunc_wrapper)
--18357-- REDIR: 0x46565c10 (__memcmp_ssse3) redirected to 0x4009fd0 (bcmp)
1
1
1
1
1
1
1
one
five
ten
twenty
twenty-five
thirty
One-hundred
Delete
--18357-- REDIR: 0x46a221d0 (operator delete(void*)) redirected to 0x4006b10 (operator delete(void*))
Delete
Delete
Delete
--18357-- REDIR: 0x464943e0 (free) redirected to 0x4006e80 (free)
==18357== 
==18357== HEAP SUMMARY:
==18357==     in use at exit: 86 bytes in 3 blocks
==18357==   total heap usage: 12 allocs, 9 frees, 375 bytes allocated
==18357== 
==18357== Searching for pointers to 3 not-freed blocks
==18357== Checked 97,132 bytes
==18357== 
==18357== LEAK SUMMARY:
==18357==    definitely lost: 48 bytes in 1 blocks
==18357==    indirectly lost: 38 bytes in 2 blocks
==18357==      possibly lost: 0 bytes in 0 blocks
==18357==    still reachable: 0 bytes in 0 blocks
==18357==         suppressed: 0 bytes in 0 blocks
==18357== Rerun with --leak-check=full to see details of leaked memory
==18357== 
==18357== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)
==18357== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)
-bash-4.2$ 

Answer 1

最好的办法是将原始指针替换为 std::unique_ptr< Elem > .这样你根本不需要析构函数。当心Elem::parent可能是非拥有指针，因此不应被替换。