From dbf3ad101d9e515850fe3fd32492d4f0288bc943 Mon Sep 17 00:00:00 2001 From: Max Wash Date: Tue, 24 Jan 2023 21:26:22 +0000 Subject: [PATCH] sandbox: btree: deletion fixup bugfix --- sandbox/base/main.c | 31 +++++++++++---- sandbox/btree/btree.c | 87 +++++++++++++++++++++++++++---------------- 2 files changed, 78 insertions(+), 40 deletions(-) diff --git a/sandbox/base/main.c b/sandbox/base/main.c index 08242fa..37f7ec6 100644 --- a/sandbox/base/main.c +++ b/sandbox/base/main.c @@ -10,7 +10,7 @@ #include #include -#define NR_BTREE_NODES 13 +#define NR_BTREE_NODES 32 /* we're working with 512MiB of simulated system RAM */ #define MEMORY_SIZE_MB 512 @@ -130,10 +130,28 @@ static int memory_test(void) void btree_print(btree_node_t *node, int depth) { + if (depth > 10) { + for (int i = 0; i < depth; i++) { + fputs(" ", stdout); + } + + printf("OVERFLOW\n"); + return; + } + if (!node) { return; } + if (node->b_parent && node != node->b_parent->b_left && node != node->b_parent->b_right) { + for (int i = 0; i < depth; i++) { + fputs(" ", stdout); + } + + printf("BAD PARENT [%llu]\n", node->b_key); + return; + } + if (node) { btree_print(node->b_right, depth + 1); } @@ -146,9 +164,12 @@ void btree_print(btree_node_t *node, int depth) if (node->b_parent) { if (node == node->b_parent->b_left) { printf("\\ "); - } else { + } else if (node == node->b_parent->b_right) { printf("/ "); + } else { + printf("? "); } + } printf("%llu (h:%d)\n", node->b_key, node->b_height); @@ -172,7 +193,7 @@ static int btree_avl_validate(btree_node_t *x) } if (!x->b_left && !x->b_right) { - return 1; + return x->b_height == 1 ? 1 : -1; } int left = 0, right = 0; @@ -241,10 +262,6 @@ static int btree_test(void) printf("deleting node #%d: %llu\n", i, nodes[i].b_key); printf("#######################\n"); - if (nodes[i].b_key == 89) { - printf("brk\n"); - } - btree_delete(&tree, &nodes[i]); btree_print(tree.b_root, 0); diff --git a/sandbox/btree/btree.c b/sandbox/btree/btree.c index 206426d..3526a77 100644 --- a/sandbox/btree/btree.c +++ b/sandbox/btree/btree.c @@ -222,15 +222,18 @@ static void delete_fixup(btree_t *tree, btree_node_t *w) int nr_rotations = 0; while (z) { + printf("bf(z)=%d\n", bf(z)); + printf("bf(z->b_left)=%d\n", bf(z->b_left)); + if (bf(z) > 1) { - if (bf(z->b_left) <= 0) { + if (bf(z->b_right) >= 0) { rotate_left(tree, z); update_height_to_root(z); } else { - rotate_double_left(tree, z); + rotate_double_left(tree, z); // <== } } else if (bf(z) < -1) { - if (bf(z->b_right) > 0) { + if (bf(z->b_left) <= 0) { rotate_right(tree, z); update_height_to_root(z); } else { @@ -354,62 +357,78 @@ static btree_node_t *replace_node_with_one_subtree(btree_t *tree, btree_node_t * return w; } -static btree_node_t *replace_node_with_two_subtrees(btree_t *tree, btree_node_t *node) +static btree_node_t *replace_node_with_two_subtrees(btree_t *tree, btree_node_t *z) { debug_msg("remove_node_with_two_subtrees()\n"); - btree_node_t *cur = node->b_left; - while (cur->b_right) { - cur = cur->b_right; + /* x will replace z */ + btree_node_t *x = z->b_left; + + while (x->b_right) { + x = x->b_right; } - btree_node_t *p = cur->b_parent; - btree_node_t *k = p; + /* y is the node that will replace x (if x has a left child) */ + btree_node_t *y = x->b_left; - if (IS_LEFT_CHILD(p, cur)) { - p->b_left = NULL; - } else { - p->b_right = NULL; + /* w is the starting point for the height update and fixup */ + btree_node_t *w = x; + if (w->b_parent != z) { + w = w->b_parent; } - p = node->b_parent; - - if (p) { - if (IS_LEFT_CHILD(p, node)) { - p->b_left = cur; - } else { - p->b_right = cur; - } + if (y) { + w = y; } - cur->b_left = node->b_left; - cur->b_right = node->b_right; - cur->b_height = node->b_height; - cur->b_parent = p; - btree_node_t *w = cur; - - if (!p) { - tree->b_root = cur; + if (IS_LEFT_CHILD(x->b_parent, x)) { + x->b_parent->b_left = y; + } else if (IS_RIGHT_CHILD(x->b_parent, x)) { + x->b_parent->b_right = y; } - if (tree->b_root->b_left) { - tree->b_root->b_left->b_parent = tree->b_root; + if (y) { + y->b_parent = x->b_parent; } - if (tree->b_root->b_right) { - tree->b_root->b_right->b_parent = tree->b_root; + if (IS_LEFT_CHILD(z->b_parent, z)) { + z->b_parent->b_left = x; + } else if (IS_RIGHT_CHILD(z->b_parent, z)) { + z->b_parent->b_right = x; } + x->b_parent = z->b_parent; + x->b_left = z->b_left; + x->b_right = z->b_right; + + if (x->b_left) { + x->b_left->b_parent = x; + } + + if (x->b_right) { + x->b_right->b_parent = x; + } + + if (!x->b_parent) { + tree->b_root = x; + } + + btree_node_t *cur = w; while (cur) { update_height(cur); cur = cur->b_parent; } + printf("w=%llu, h:%u\n", w->b_key, w->b_height); return w; } void btree_delete(btree_t *tree, btree_node_t *node) { + if (!node->b_owner) { + return; + } + assert(node->b_owner == tree); btree_node_t *w = NULL; @@ -421,6 +440,8 @@ void btree_delete(btree_t *tree, btree_node_t *node) w = replace_node_with_two_subtrees(tree, node); } + btree_print(tree->b_root, 0); + if (w) { delete_fixup(tree, w); }