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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