[337] | 1 | #include <stdlib.h>
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| 2 | #include <search.h>
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| 3 |
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| 4 | /*
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| 5 | avl tree implementation using recursive functions
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| 6 | the height of an n node tree is less than 1.44*log2(n+2)-1
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| 7 | (so the max recursion depth in case of a tree with 2^32 nodes is 45)
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| 8 | */
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| 9 |
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| 10 | struct node {
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| 11 | const void *key;
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| 12 | struct node *left;
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| 13 | struct node *right;
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| 14 | int height;
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| 15 | };
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| 16 |
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| 17 | static int delta(struct node *n) {
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| 18 | return (n->left ? n->left->height:0) - (n->right ? n->right->height:0);
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| 19 | }
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| 20 |
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| 21 | static void updateheight(struct node *n) {
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| 22 | n->height = 0;
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| 23 | if (n->left && n->left->height > n->height)
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| 24 | n->height = n->left->height;
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| 25 | if (n->right && n->right->height > n->height)
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| 26 | n->height = n->right->height;
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| 27 | n->height++;
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| 28 | }
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| 29 |
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| 30 | static struct node *rotl(struct node *n) {
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| 31 | struct node *r = n->right;
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| 32 | n->right = r->left;
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| 33 | r->left = n;
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| 34 | updateheight(n);
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| 35 | updateheight(r);
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| 36 | return r;
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| 37 | }
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| 38 |
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| 39 | static struct node *rotr(struct node *n) {
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| 40 | struct node *l = n->left;
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| 41 | n->left = l->right;
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| 42 | l->right = n;
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| 43 | updateheight(n);
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| 44 | updateheight(l);
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| 45 | return l;
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| 46 | }
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| 47 |
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| 48 | static struct node *balance(struct node *n) {
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| 49 | int d = delta(n);
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| 50 |
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| 51 | if (d < -1) {
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| 52 | if (delta(n->right) > 0)
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| 53 | n->right = rotr(n->right);
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| 54 | return rotl(n);
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| 55 | } else if (d > 1) {
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| 56 | if (delta(n->left) < 0)
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| 57 | n->left = rotl(n->left);
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| 58 | return rotr(n);
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| 59 | }
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| 60 | updateheight(n);
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| 61 | return n;
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| 62 | }
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| 63 |
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| 64 | static struct node *find(struct node *n, const void *k,
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| 65 | int (*cmp)(const void *, const void *))
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| 66 | {
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| 67 | int c;
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| 68 |
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| 69 | if (!n)
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| 70 | return 0;
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| 71 | c = cmp(k, n->key);
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| 72 | if (c == 0)
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| 73 | return n;
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| 74 | if (c < 0)
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| 75 | return find(n->left, k, cmp);
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| 76 | else
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| 77 | return find(n->right, k, cmp);
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| 78 | }
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| 79 |
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| 80 | static struct node *insert(struct node *n, const void *k,
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| 81 | int (*cmp)(const void *, const void *), struct node **found)
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| 82 | {
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| 83 | struct node *r;
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| 84 | int c;
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| 85 |
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| 86 | if (!n) {
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| 87 | n = malloc(sizeof *n);
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| 88 | if (n) {
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| 89 | n->key = k;
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| 90 | n->left = n->right = 0;
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| 91 | n->height = 1;
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| 92 | }
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| 93 | *found = n;
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| 94 | return n;
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| 95 | }
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| 96 | c = cmp(k, n->key);
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| 97 | if (c == 0) {
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| 98 | *found = n;
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| 99 | return 0;
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| 100 | }
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| 101 | r = insert(c < 0 ? n->left : n->right, k, cmp, found);
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| 102 | if (r) {
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| 103 | if (c < 0)
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| 104 | n->left = r;
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| 105 | else
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| 106 | n->right = r;
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| 107 | r = balance(n);
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| 108 | }
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| 109 | return r;
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| 110 | }
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| 111 |
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| 112 | static struct node *remove_rightmost(struct node *n, struct node **rightmost)
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| 113 | {
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| 114 | if (!n->right) {
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| 115 | *rightmost = n;
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| 116 | return n->left;
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| 117 | }
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| 118 | n->right = remove_rightmost(n->right, rightmost);
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| 119 | return balance(n);
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| 120 | }
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| 121 |
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| 122 | static struct node *remove(struct node **n, const void *k,
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| 123 | int (*cmp)(const void *, const void *), struct node *parent)
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| 124 | {
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| 125 | int c;
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| 126 |
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| 127 | if (!*n)
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| 128 | return 0;
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| 129 | c = cmp(k, (*n)->key);
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| 130 | if (c == 0) {
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| 131 | struct node *r = *n;
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| 132 | if (r->left) {
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| 133 | r->left = remove_rightmost(r->left, n);
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| 134 | (*n)->left = r->left;
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| 135 | (*n)->right = r->right;
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| 136 | *n = balance(*n);
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| 137 | } else
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| 138 | *n = r->right;
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| 139 | free(r);
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| 140 | return parent;
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| 141 | }
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| 142 | if (c < 0)
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| 143 | parent = remove(&(*n)->left, k, cmp, *n);
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| 144 | else
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| 145 | parent = remove(&(*n)->right, k, cmp, *n);
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| 146 | if (parent)
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| 147 | *n = balance(*n);
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| 148 | return parent;
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| 149 | }
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| 150 |
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| 151 | void *tdelete(const void *restrict key, void **restrict rootp,
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| 152 | int(*compar)(const void *, const void *))
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| 153 | {
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| 154 | if (!rootp)
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| 155 | return 0;
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| 156 | struct node *n = *rootp;
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| 157 | struct node *ret;
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| 158 | /* last argument is arbitrary non-null pointer
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| 159 | which is returned when the root node is deleted */
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| 160 | ret = remove(&n, key, compar, n);
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| 161 | *rootp = n;
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| 162 | return ret;
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| 163 | }
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| 164 |
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| 165 | void *tfind(const void *key, void *const *rootp,
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| 166 | int(*compar)(const void *, const void *))
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| 167 | {
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| 168 | if (!rootp)
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| 169 | return 0;
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| 170 | return find(*rootp, key, compar);
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| 171 | }
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| 172 |
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| 173 | void *tsearch(const void *key, void **rootp,
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| 174 | int (*compar)(const void *, const void *))
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| 175 | {
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| 176 | struct node *update;
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| 177 | struct node *ret;
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| 178 | if (!rootp)
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| 179 | return 0;
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| 180 | update = insert(*rootp, key, compar, &ret);
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| 181 | if (update)
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| 182 | *rootp = update;
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| 183 | return ret;
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| 184 | }
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| 185 |
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| 186 | static void walk(const struct node *r, void (*action)(const void *, VISIT, int), int d)
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| 187 | {
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| 188 | if (r == 0)
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| 189 | return;
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| 190 | if (r->left == 0 && r->right == 0)
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| 191 | action(r, leaf, d);
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| 192 | else {
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| 193 | action(r, preorder, d);
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| 194 | walk(r->left, action, d+1);
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| 195 | action(r, postorder, d);
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| 196 | walk(r->right, action, d+1);
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| 197 | action(r, endorder, d);
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| 198 | }
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| 199 | }
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| 200 |
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| 201 | void twalk(const void *root, void (*action)(const void *, VISIT, int))
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| 202 | {
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| 203 | walk(root, action, 0);
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| 204 | }
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