Merge pull request matthewsamuel95#535 from koneko096/master

Add treap data structure

Author: matthewsamuel95

Data Structures/Treap/treap.cpp

@@ -0,0 +1,111 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+typedef struct node {
+    int val,prior,size;
+    struct node *l,*r;
+} node;
+
+typedef node* pnode;
+
+int sz (pnode t) {
+    return t ? t->size : 0;
+}
+
+void upd_sz (pnode t) {
+    if (t) {
+        t->size = sz(t->l) + 1 + sz(t->r);
+    }
+}
+
+pnode find (pnode t, int key) {
+    if (t == NULL || t->val == key) {
+        return t;
+    }
+
+    return find(t->val < key ? t->r : t->l, key);
+}
+
+void split (pnode t, pnode &l, pnode &r, int key) {
+    if (!t) {
+        l = r = NULL;
+    }
+    else if (t->val <= key) {
+        split(t->r, t->r, r, key);
+        l = t;
+    }
+    else {
+        split(t->l, l, t->l, key);
+        r = t;
+    }
+
+    upd_sz(t);
+}
+
+void merge (pnode &t, pnode l, pnode r) {
+    if (!l || !r) {
+        t = l?l:r;
+    }
+    else if (l->prior > r->prior) {
+        merge(l->r, l->r, r);
+        t = l;
+    }
+    else {
+        merge(r->l, l, r->l);
+        t = r;
+    }
+
+    upd_sz(t);
+}
+
+void insert (pnode &t, pnode it) {
+    if (!t) {
+        t = it;
+    }    
+    else if (it->prior > t->prior) {
+        split(t, it->l, it->r, it->val);
+        t = it;
+    }
+    else {
+        insert(t->val <= it->val ? t->r : t->l, it);
+    }
+
+    upd_sz(t);
+}
+
+void erase (pnode &t, int key) {
+    pnode p = find(t, key);
+    if (p == NULL) {
+        return;
+    }
+    
+    pnode temp = t;
+    merge(t, p->l, p->r);
+    free(temp);
+
+    upd_sz(t);
+}
+
+pnode init (int val) {
+    pnode ret = (pnode)malloc(sizeof(node));
+    ret->val = val;
+    ret->size = 1;
+    ret->prior = rand();
+    ret->l = ret->r = NULL;
+    return ret;
+}
+
+int main() {
+    pnode t = init(4);
+    insert(t, init(19));
+    insert(t, init(8));
+    insert(t, init(27));
+    insert(t, init(20));
+    insert(t, init(12));
+    insert(t, init(15));
+    insert(t, init(6));
+    insert(t, init(7));
+    insert(t, init(8));
+  
+    return 0;
+}

README.md

@@ -54,6 +54,7 @@ ACM-ICPC Algorithms is a collection of important algorithms and data structures
    * [Singly Linked List](/Data%20Structures/SinglyLinkedList)
    * [Stack](/Data%20Structures/Stack)
    * [Segment Tree](/Data%20Structures/Segment%20Tree)
+   * [Treap](/Data%20Structures/Treap)
    * [Trie](/Data%20Structures/Trie)
 * [Dynamic Programming](/DP)
    * [Coin Change](/DP/Coin%20Change%20Problem)