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PORed Black Tree - deletion
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5967117
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0
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1
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3
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2011-05-11T15:52:19.453
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2015-08-29T17:33:24.707
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2015-08-29T17:33:24.707
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4370109
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1
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1
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3113
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text
Body
I've implemented delete function for RBT (basing on Cormen), it looks like it works but test for deletion + printing tree in preorder gives me wrong answer. I spent few hours looking what may be wrong but couldn't find anything... Here's func to print tree in preorder: <pre><code>void print_out(rbt_node *root, rbt_node *NIL) { if(root != NIL) { printf("%d %s ", root->key, root->data.c_str()); if(root->color == BLACK) printf("black "); else printf("red "); if(root->parent != NIL) printf("%d ",root->parent->key); else printf("- "); if(root->left != NIL) printf("%d ",root->left->key); else printf("- "); if(root->right != NIL) printf("%d ",root->right->key); else printf("- "); printf("\n"); print_out(root->left, NIL); if(root->right != NIL) { print_out(root->right, NIL); } } } </code></pre> Here is rest of important stuff for deletion: <pre><code>rbt_node *NIL = new rbt_node; NIL->color = BLACK; NIL->left = NIL->parent = NIL->right = NIL; rbt_node *tree_minimum(rbt_node *node, rbt_node *NIL) { while(node->left != NIL) node = node->left; return node; } rbt_node *tree_succesor(rbt_node *node, rbt_node *NIL) { if(node->right != NIL) return tree_minimum(node->right, NIL); rbt_node *helper = node->parent; while(helper != NIL && node == helper->right) { node = helper; helper = helper->parent; } return helper; } void delete_fixup(rbt_node *&root, rbt_node *&target, rbt_node *NIL) { rbt_node *helper = NIL; while(target != root && target->color == BLACK) { if(target == target->parent->left) { helper = target->parent->right; if(helper->color == RED) { helper->color = BLACK; target->parent->color = RED; left_rotate(root, target->parent, NIL); helper = target->parent->right; } if(helper->left->color == BLACK && helper->right->color == BLACK) { helper->color = RED; target = target->parent; } else if(helper->right->color== BLACK) { helper->left->color = BLACK; helper->color = RED; right_rotate(root, helper, NIL); helper = target->parent->right; } else { helper->color = target->parent->color; target->parent->color = BLACK; helper->right->color = BLACK; left_rotate(root, target->parent, NIL); target = root; } } else { helper = target->parent->left; if(helper->color == RED) { helper->color = BLACK; target->parent->color = RED; right_rotate(root, target->parent, NIL); helper = target->parent->left; } if(helper->right->color == BLACK && helper->left->color == BLACK) { helper->color = RED; target = target->parent; } else if(helper->left->color== BLACK) { helper->right->color = BLACK; helper->color = RED; left_rotate(root, helper, NIL); helper = target->parent->left; } else { helper->color = target->parent->color; target->parent->color = BLACK; helper->left->color = BLACK; right_rotate(root, target->parent, NIL); target = root; } } } target->color = BLACK; } void rbt_delete(rbt_node *&root, int key, rbt_node *NIL) { rbt_node *victim = to_delete(root, key, NIL); if(victim != NIL) { rbt_node *help_one = NIL; rbt_node *help_two = NIL; if(victim->left == NIL || victim->right == NIL) help_one = victim; else help_one = tree_succesor(victim, NIL); if(help_one->left != NIL) help_two = help_one->left; else help_two = help_one->right; help_two->parent = help_one->parent; if(help_one->parent == NIL) root = help_two; else if(help_one == help_one->parent->left) help_one->parent->left = help_two; else help_two->parent->right = help_two; if(help_one != victim) { victim->key = help_one->key; victim->data = help_one->data; } if(help_one->color == BLACK) delete_fixup(root, help_two, NIL); } root->color = BLACK; } </code></pre>
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<c++><red-black-tree>
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Red Black Tree - deletion
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