Leftist heap

Author: Takanori MAEHARA

data_structure/leftist_heap.cc

@@ -0,0 +1,84 @@
+//
+// Leftist Heap
+//
+// Description:
+//
+//   Leftist heap is a heap data structure that allows
+//   the meld (merge) operation in O(log n) time.
+//   Use this for persistent heaps.
+//
+// Complexity:
+//
+//   O(1) for top, O(log n) for push/pop/meld
+//
+// g++ -std=c++17 -O3 -fmax-errors=1 -fsanitize=undefined
+#include <bits/stdc++.h>
+
+using namespace std;
+
+#define fst first
+#define snd second
+#define all(c) ((c).begin()), ((c).end())
+#define TEST(s) if (!(s)) { cout << __LINE__ << " " << #s << endl; exit(-1); }
+
+template <class T>
+struct LeftistHeap {
+  struct Node {
+    T key;
+    Node *left = 0, *right = 0;
+    int dist = 0;
+  } *root = 0;
+  static Node *merge(Node *x, Node *y) {
+    if (!x) return y;
+    if (!y) return x;
+    if (x->key > y->key) swap(x, y);
+    x->right = merge(x->right, y);
+    if (!x->left || x->left->dist < x->dist) swap(x->left, x->right);
+    x->dist = (x->right ? x->right->dist : 0) + 1;
+    return x;
+  }
+  void push(T key) { root = merge(root, new Node({key})); }
+  void pop() { root = merge(root->left, root->right); }
+  T top() { return root->key; }
+};
+
+//
+// Persistent Implementaiton. (allow copy)
+//
+template <class T>
+struct PersistentLeftistHeap {
+  struct Node {
+    T key;
+    Node *left = 0, *right = 0;
+    int dist = 0;
+  } *root = 0;
+  static Node *merge(Node *x, Node *y) {
+    if (!x) return y;
+    if (!y) return x;
+    if (x->key > y->key) swap(x, y);
+    x = new Node(*x);
+    x->right = merge(x->right, y);
+    if (!x->left || x->left->dist < x->dist) swap(x->left, x->right);
+    x->dist = (x->right ? x->right->dist : 0) + 1;
+    return x;
+  }
+  void push(T key) { root = merge(root, new Node({key})); }
+  void pop() { root = merge(root->left, root->right); }
+  T top() { return root->key; }
+};
+
+int main() {
+  PersistentLeftistHeap<int> heap;
+  heap.push(3);
+  heap.push(1);
+  heap.push(4);
+  heap.push(1);
+  heap.push(5);
+  cout << heap.top() << endl; heap.pop();
+  cout << heap.top() << endl; heap.pop();
+  auto temp = heap;
+  cout << heap.top() << endl; heap.pop();
+  cout << heap.top() << endl; heap.pop();
+  cout << temp.top() << endl; temp.pop();
+  cout << temp.top() << endl; temp.pop();
+}