我有以下工作代码,用于红黑树旋转。
void BalancedTree::rotateLeft(Node* & x){
37 Node* y = x->right;
38
39 x->right = y->left;//slice y's left child
40 x->right->parent = x;
41
42 y->left = x;//switch x and y's parentship
43 Node* xp = x->parent;//for some reason, y->parent = x->parent causes logic
errors.
44 x->parent = y;
45 y->parent = xp;
46
47 if (y->parent == nil) root = y;//fix grandparent
48 else if (y->parent->parent->left == x) y->parent->parent->left = y;
49 else y->parent->parent->right = y;
50 }
当第43和45行被替换为(保持44)时
y->parent = x->parent
或者,只是交换第44和45行,改变了节点指针x的内容。我想要做的就是:更改Node中的指针(父项)(由y指示),并让它指向x的父项。
节点结构是:
struct Node{
Node* parent;
Node* left;
Node* right;
int value;
};
我错过了什么吗?指针的基本属性?
编辑:第313页Cormen的算法导论
LEFT-ROTATE(T, x)
1 y = x.right
2 x.right = y.left
3 if y.left != T.nil
4 y.left.p = x
5 y.p = x.p
6 if x.p == T.nil
7 T.root = y
8 elseif x == x.p.left
9 x.p.left = y
10 else x.p.right = y
11 y.left = x
12 x.p = y
EDIT2:以下代码不起作用:
36 void BalancedTree::rotateLeft(Node* & x){
37 Node* y = x->right;
38
39 x->right = y->left;//slice y's left child
40 x->right->parent = x;
41
42 y->left = x;//switch x and y's parentship
43 y->parent = x->parent;
44 x->parent = y;
45
46
47 if (y->parent == nil) root = y;//fix grandparent
48 else if (y->parent->parent->left == x) y->parent->parent->left = y;
49 else y->parent->parent->right = y;
50 }
答案 0 :(得分:0)
您提供的两个版本的代码确实是等效的。但是,您对此算法的实现与Cormen参考中所写的算法几乎没有关系。您的代码应为:
void BalancedTree::rotateLeft(Node* & x){
Node* y = x->right;
x->right = y->left;
if (y->left != nil)
y->left->parent = x;
y->parent = x->parent;
if (x->parent == nil)
root = y;
else if (x == x->parent->left)
x->parent->left = y;
else
x->parent->right = y;
y->left = x;
x->parent = y;
}