Question

我在C中写了AVL Tree实现。我有其他功能，但当我尝试插入一些值时出现错误。这是我的插入函数，旋转和主要的代码。我正在使用RR，LL，RL，LR旋转来平衡树。

代码：

struct avl_tree {
int key;
int bf;
struct avl_tree *up;
struct avl_tree *left;
struct avl_tree *right;
};

typedef struct avl_tree node;


void deleteTree(node *tree)
{
    if(tree)
    {
        deleteTree(tree->left);
        deleteTree(tree->right);
        free(tree);
    }
}

void RR(node **tree, node *A)
{
node *B = A->right;
node *p = A->up;

A->right = B->left;

if(A->right)
{
    A->right->up = A;
}

B->left = A;
B->up = p;
A->up = B;

if(p)
{
    if(p->left == A) p->left = B;
    else p->right = B;
}
else *tree = B;

if(B->bf == -1)
{
    A->bf = B->bf = 0;
}
else
{
    A->bf = -1;
    B->bf = 1;
}
}


void LL(node **tree, node *A)
{
node *B = A->left;
node *p = A->up;

A->left = B->right;

if(A->left)
{
    A->left->up = A;
}

B->right = A;
B->up = p;
A->up = B;

if(p)
{
    if(p->left == A) p->left = B;
    else p->right = B;
}
else *tree = B;

if(B->bf == 1)
{
    A->bf = B->bf = 0;
}
else
{
    A->bf = 1;
    B->bf = -1;
}
}


void RL(node **tree, node *A)
{
node *B = A->right;
node *C = B->left;
node *p = A->up;

B->left = C->right;

if(B->left)
{
    B->left->up = B;
}       

A->right = C->left;

if(A->right)
{
    A->right->up = A;
}       

C->left = A;
C->right = B;
A->up = B->up = C;
C->up = p;

if(p)
{
    if(p->left == A) p->left = C;
    else p->right = C;
}
else *tree = C;

if(C->bf == -1) A->bf = 1;
else A->bf = 0;

if(C->bf == 1) B->bf = -1;
else B->bf = 0;

C->bf = 0;
}

void LR(node **tree, node *A)
{
node *B = A->left;
node *C = B->right;
node *p = A->up;

B->right = C->left;

if(B->right)
{
    B->right->up = B;
}

A->left = C->right;

if(A->left)
{
    A->left->up = A;
}       

C->right = A;
C->left = B;
A->up = B->up = C;
C->up = p;


if(p)
{
    if(p->left == A) p->left = C;
    else p->right = C;
}
else *tree = C;

if(C->bf == 1) A->bf = -1;
else A->bf = 0;

if(C->bf == -1) B->bf =1;
else B->bf = 0;

C->bf = 0;
}

void insert(node **tree, int k)
{
node *w; 
node *p;
node *r;
bool t;

w = (node*)malloc(sizeof(node));
w->left = w->right = w->up = NULL;
w->key = k;
w->bf = 0;

/* 1. Insert to AVL */
p = *tree; 

if(!p)
{
    *tree = w;
}
else 
{
    while(true)
    {
        if(k < p->key)
        {
            if(!p->left)
            {
                p->left = w;
                break;
            };

            p = p->left;
        }
        else
        {
            if(!p->right)
            {
                p->right = w;
                break;
            };

            p = p->right;
        }

    w->up = p;

/* 2. Balance AVL */
    if(p->bf) p->bf = 0;
    else 
    {
        if(p->left == w) p->bf = 1;
        else p->bf = -1;

        r = p->up;

        t = false;
        while(r)
        {
            if(r->bf)
            {
                t = true;
                break;
            };

            if(r->left == p) r->bf = 1;
            else r->bf = -1;

            p = r;
            r = r->up;
        }

        if(t)
        {
            if(r->bf == 1)
            {
                if(r->right == p) r->bf = 0;
                else if(p->bf == -1) LR(tree, r);
                else LL(tree, r);
            }
            else
            {
                if(r->left == p) r->bf = 0;
                else if(p->bf == 1) RL(tree, r);
                else RR(tree, r);
            }
        }
    }
    }
}
}

主：

node *root;
root = NULL;


char str[100];
int n, x, i;

scanf("%d", &n);

for(i = 0; i<=n; i++)
{
    fgets(str, sizeof str, stdin);

    if (!strncmp(str, "insert", 6)) 
    {
        sscanf(str,"%*[^0-9]%d", &x);
        insert(&root, x);
        str[0] = '\0';          
    }
}

return 0;

输入：

29
insert 15
insert 41
insert 63
insert 99
insert 91
insert 55
insert 31
insert 82
insert 1
insert 90
insert 20
insert 52
insert 80
insert 99
insert 89
insert 32
insert 78 
insert 25
insert 55
insert 48
insert 33
insert 9
insert 80
insert 54
insert 87
insert 35
insert 33
insert 38
insert 78

尝试使用LR旋转插入值52后出错，我不知道为什么。

编辑：

insert 52

Program received signal SIGSEGV, Segmentation fault.
0x0000000000400bfd in LR ()
(gdb) print
The history is empty.
(gdb) where
#0  0x0000000000400bfd in LR ()
#1  0x0000000000400f08 in insert ()
#2  0x0000000000401503 in main ()

编辑2：

clang -Wall -Wextra -std=c99 --analyze Alg3.c 
Alg3.c:33:13: warning: Access to field 'left' results in a dereference of a null
  pointer (loaded from variable 'B')
    A->right = B->left;
               ^~~~~~~
Alg3.c:101:12: warning: Access to field 'left' results in a dereference of a
  null pointer (loaded from variable 'B')
    node *C = B->left;
              ^~~~~~~
Alg3.c:394:10: warning: Access to field 'bf' results in a dereference of a null
  pointer (loaded from variable 't')
                                    if(!(t->bf))
                                        ^~~~~~~
3 warnings generated.

Answer 1

while (true)中的insert()循环未结束：

       }
    // The while (true) loop should end here, but it doesn't...
    w->up = p;

/* 2. Balance AVL */

将值插入AVL树

1 个答案: