| 1 | #include "avl.h" |
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| 2 | #include "avl-private.h" |
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| 3 | #include <stdlib.hfa> |
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| 4 | |
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| 5 | // swaps the data within two tree nodes |
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| 6 | forall(K | Comparable(K), V) |
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| 7 | void node_swap(tree(K, V) * t, tree(K, V) * t2){ |
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| 8 | swap( t->key, t2->key); |
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| 9 | swap( t->value, t2->value); |
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| 10 | } |
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| 11 | |
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| 12 | // go left as deep as possible from within the right subtree |
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| 13 | forall(K | Comparable(K), V) |
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| 14 | tree(K, V) * find_successor(tree(K, V) * t){ |
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| 15 | tree(K, V) * find_successor_helper(tree(K, V) * t){ |
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| 16 | // go left as deep as possible, return the last node |
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| 17 | if (empty(t->left)){ |
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| 18 | return t; |
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| 19 | } else { |
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| 20 | return find_successor_helper(t->left); |
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| 21 | } |
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| 22 | } |
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| 23 | return find_successor_helper(t->right); |
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| 24 | } |
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| 25 | |
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| 26 | // cleanup - don't want to deep delete, so set children to NULL first. |
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| 27 | forall(K | Comparable(K), V) |
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| 28 | void deleteSingleNode(tree(K, V) * t) { |
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| 29 | t->left = NULL; |
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| 30 | t->right = NULL; |
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| 31 | delete(t); |
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| 32 | } |
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| 33 | |
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| 34 | // does the actual remove operation once we've found the node in question |
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| 35 | forall(K | Comparable(K), V) |
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| 36 | tree(K, V) * remove_node(tree(K, V) * t){ |
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| 37 | // is the node a leaf? |
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| 38 | if (empty(t->left) && empty(t->right)){ |
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| 39 | // yes, just delete this node |
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| 40 | delete(t); |
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| 41 | return NULL; |
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| 42 | } else if (empty(t->left)){ |
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| 43 | // if the left is empty, there is only one child -> move right up |
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| 44 | node_swap(t, t->right); |
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| 45 | tree(K, V) * tmp = t->right; |
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| 46 | |
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| 47 | // relink tree |
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| 48 | t->left = tmp->left; |
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| 49 | t->right = tmp->right; |
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| 50 | |
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| 51 | setParent(t->left, t); |
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| 52 | setParent(t->right, t); |
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| 53 | deleteSingleNode(tmp); |
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| 54 | return t; |
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| 55 | } else if (empty(t->right)){ |
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| 56 | // if the right is empty, there is only one child -> move left up |
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| 57 | node_swap(t, t->left); |
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| 58 | tree(K, V) * tmp = t->left; |
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| 59 | |
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| 60 | // relink tree |
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| 61 | t->left = tmp->left; |
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| 62 | t->right = tmp->right; |
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| 63 | |
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| 64 | setParent(t->left, t); |
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| 65 | setParent(t->right, t); |
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| 66 | deleteSingleNode(tmp); |
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| 67 | return t; |
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| 68 | } else { |
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| 69 | // swap with the successor |
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| 70 | tree(K, V) * s = find_successor(t); |
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| 71 | tree(K, V) * parent = s->parent; |
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| 72 | |
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| 73 | if (parent->left == s){ |
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| 74 | parent->left = s->right; |
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| 75 | } else { |
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| 76 | assert(parent->right == s); |
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| 77 | parent->right = s->right; |
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| 78 | } |
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| 79 | setParent(s->right, parent); |
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| 80 | node_swap(t, s); |
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| 81 | deleteSingleNode(s); |
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| 82 | return t; |
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| 83 | } |
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| 84 | } |
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| 85 | |
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| 86 | // finds the node that needs to be removed |
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| 87 | forall(K | Comparable(K), V) |
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| 88 | tree(K, V) * remove_helper(tree(K, V) * t, K key, int * worked){ |
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| 89 | if (empty(t)){ |
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| 90 | // did not work because key was not found |
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| 91 | // set the status variable and return |
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| 92 | *worked = 1; |
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| 93 | } else if (t->key == key) { |
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| 94 | t = remove_node(t); |
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| 95 | } else if (t->key < key){ |
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| 96 | t->right = remove_helper(t->right, key, worked); |
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| 97 | } else { |
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| 98 | // t->key > key |
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| 99 | t->left = remove_helper(t->left, key, worked); |
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| 100 | } |
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| 101 | // try to fix after deleting |
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| 102 | if (! empty(t)) { |
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| 103 | t = tryFix(t); |
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| 104 | } |
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| 105 | return t; |
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| 106 | } |
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| 107 | |
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| 108 | forall(K | Comparable(K), V) |
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| 109 | int remove(tree(K, V) ** t, K key){ |
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| 110 | int worked = 0; |
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| 111 | tree(K, V) * newTree = remove_helper(*t, key, &worked); |
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| 112 | *t = newTree; |
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| 113 | return worked; |
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| 114 | } |
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| 115 | |
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| 116 | // Local Variables: // |
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| 117 | // tab-width: 4 // |
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| 118 | // End: // |
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