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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