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| 1 | +#include <bits/stdc++.h> |
| 2 | +#define ll long long |
| 3 | +#define MOD 1000000007 |
| 4 | +using namespace std; |
| 5 | + |
| 6 | +// structure representing a treap node |
| 7 | +struct node { |
| 8 | + ll key; |
| 9 | + ll priority; |
| 10 | + node* left; |
| 11 | + node* right; |
| 12 | + node* parent; |
| 13 | + |
| 14 | + node(ll data) { |
| 15 | + key = data; |
| 16 | + priority = (1LL * rand()) % MOD; |
| 17 | + left = right = parent = NULL; |
| 18 | + } |
| 19 | +}; |
| 20 | + |
| 21 | +// function to left-rotate the subtree rooted at x |
| 22 | +void left_rotate(node* &root, node* x) { |
| 23 | + node* y = x->right; |
| 24 | + x->right = y->left; |
| 25 | + |
| 26 | + if (y->left != NULL) { |
| 27 | + y->left->parent = x; |
| 28 | + } |
| 29 | + y->parent = x->parent; |
| 30 | + if (x->parent == NULL) { |
| 31 | + root = y; |
| 32 | + } |
| 33 | + else if (x->key > x->parent->key) { |
| 34 | + x->parent->right = y; |
| 35 | + } |
| 36 | + else { |
| 37 | + x->parent->left = y; |
| 38 | + } |
| 39 | + |
| 40 | + y->left = x; |
| 41 | + x->parent = y; |
| 42 | +} |
| 43 | + |
| 44 | +// function to right-rotate the subtree rooted at x |
| 45 | +void right_rotate(node* &root, node* x) { |
| 46 | + node* y = x->left; |
| 47 | + x->left = y->right; |
| 48 | + |
| 49 | + if (y->right != NULL) { |
| 50 | + y->right->parent = x; |
| 51 | + } |
| 52 | + y->parent = x->parent; |
| 53 | + if (x->parent == NULL) { |
| 54 | + root = y; |
| 55 | + } |
| 56 | + else if (x->key > x->parent->key) { |
| 57 | + x->parent->right = y; |
| 58 | + } |
| 59 | + else { |
| 60 | + x->parent->left = y; |
| 61 | + } |
| 62 | + |
| 63 | + y->right = x; |
| 64 | + x->parent = y; |
| 65 | +} |
| 66 | + |
| 67 | +// function to restore min-heap property by rotations |
| 68 | +void treap_insert_fixup(node* &root, node* z) { |
| 69 | + while (z->parent != NULL && z->parent->priority > z->priority) { |
| 70 | + // if z is a right child |
| 71 | + if (z->key > z->parent->key) { |
| 72 | + left_rotate(root, z->parent); |
| 73 | + } |
| 74 | + // if z is a left child |
| 75 | + else { |
| 76 | + right_rotate(root, z->parent); |
| 77 | + } |
| 78 | + } |
| 79 | +} |
| 80 | + |
| 81 | +// function to insert a node into the treap |
| 82 | +// performs simple BST insert and calls treap_insert_fixup |
| 83 | +void insert(node* &root, ll data) { |
| 84 | + node *x = root, *y = NULL; |
| 85 | + while (x != NULL) { |
| 86 | + y = x; |
| 87 | + if (data < x->key) { |
| 88 | + x = x->left; |
| 89 | + } |
| 90 | + else { |
| 91 | + x = x->right; |
| 92 | + } |
| 93 | + } |
| 94 | + |
| 95 | + node* z = new node(data); |
| 96 | + z->parent = y; |
| 97 | + if (y == NULL) { |
| 98 | + root = z; |
| 99 | + } |
| 100 | + else if (z->key > y->key) { |
| 101 | + y->right = z; |
| 102 | + } |
| 103 | + else { |
| 104 | + y->left = z; |
| 105 | + } |
| 106 | + |
| 107 | + treap_insert_fixup(root, z); |
| 108 | +} |
| 109 | + |
| 110 | +void preorder(node* root) { |
| 111 | + if (root) { |
| 112 | + cout << root->key << " "; |
| 113 | + preorder(root->left); |
| 114 | + preorder(root->right); |
| 115 | + } |
| 116 | +} |
| 117 | + |
| 118 | +// free the allocated memory |
| 119 | +void delete_treap(node* root) { |
| 120 | + if (root) { |
| 121 | + delete_treap(root->left); |
| 122 | + delete_treap(root->right); |
| 123 | + delete root; |
| 124 | + } |
| 125 | +} |
| 126 | + |
| 127 | +int main() { |
| 128 | + node* root = NULL; |
| 129 | + int choice; |
| 130 | + ll key; |
| 131 | + while (true) { |
| 132 | + cout << "1. Insert 2. Preorder 3. Quit\n"; |
| 133 | + cin >> choice; |
| 134 | + if (choice == 1) { |
| 135 | + cout << "Enter key : "; |
| 136 | + cin >> key; |
| 137 | + insert(root, key); |
| 138 | + } |
| 139 | + else if (choice == 2) { |
| 140 | + preorder(root); |
| 141 | + cout << endl; |
| 142 | + } |
| 143 | + else { |
| 144 | + break; |
| 145 | + } |
| 146 | + } |
| 147 | + delete_treap(root); |
| 148 | + return 0; |
| 149 | +} |
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