From 22634735187479e7273c8639f5df997e856f4eec Mon Sep 17 00:00:00 2001
From: pratiamalden <pratiamalden@gmail.com>
Date: Fri, 12 Dec 2025 20:40:19 +0000
Subject: [PATCH 1/2] implement skip list

---
 Sprint-2/implement_skip_list/skip_list.py | 71 +++++++++++++++++++++++
 1 file changed, 71 insertions(+)
 create mode 100644 Sprint-2/implement_skip_list/skip_list.py

diff --git a/Sprint-2/implement_skip_list/skip_list.py b/Sprint-2/implement_skip_list/skip_list.py
new file mode 100644
index 0000000..710faad
--- /dev/null
+++ b/Sprint-2/implement_skip_list/skip_list.py
@@ -0,0 +1,71 @@
+import random
+
+
+class Node:
+    def __init__(self, value, level):
+        self.value = value
+        self.next = [None] * (level + 1) # next[i] the next node at level i
+
+
+class SkipList:
+    MAX_LEVEL = 16
+    P = 0.5
+
+    def __init__(self):
+        self.head = Node(None, self.MAX_LEVEL)
+        self.level = 0          # highest level currently in use
+
+    def _random_level(self):
+        lvl = 0
+        while random.random() < self.P and lvl < self.MAX_LEVEL:
+            lvl += 1
+        return lvl
+
+    def insert(self, value):
+        update = [None] * (self.MAX_LEVEL + 1)
+        x = self.head
+
+        # Find the place where the new value should go
+        for i in range(self.level, -1, -1):
+            while x.next[i] and x.next[i].value < value:
+                x = x.next[i]
+            update[i] = x
+
+        x0 = x.next[0]
+        if x0 and x0.value == value:
+            return
+
+        node_level = self._random_level()
+
+        if node_level > self.level:
+            for i in range(self.level + 1, node_level + 1):
+                update[i] = self.head
+            self.level = node_level
+
+        new_node = Node(value, node_level)
+        for i in range(node_level + 1):
+            new_node.next[i] = update[i].next[i]
+            update[i].next[i] = new_node
+    
+    # Check if value exists
+    def contains(self, value):
+        x = self.head
+        for lvl in range(self.level, -1, -1):
+            while x.next[lvl] and x.next[lvl].value < value:
+                x = x.next[lvl]
+
+        x = x.next[0]
+        return x is not None and x.value == value
+
+    def __contains__(self, value):
+        return self.contains(value)
+
+    def to_list(self):
+        result = []
+        x = self.head.next[0]
+        while x:
+            result.append(x.value)
+            x = x.next[0]
+        return result
+
+    

From 20b19e822200021d06ab60804549918fb2a2b746 Mon Sep 17 00:00:00 2001
From: pratiamalden <pratiamalden@gmail.com>
Date: Fri, 20 Mar 2026 12:45:19 +0000
Subject: [PATCH 2/2] Rename variables

---
 Sprint-2/implement_skip_list/skip_list.py | 44 +++++++++++------------
 1 file changed, 22 insertions(+), 22 deletions(-)

diff --git a/Sprint-2/implement_skip_list/skip_list.py b/Sprint-2/implement_skip_list/skip_list.py
index 710faad..96cc1a9 100644
--- a/Sprint-2/implement_skip_list/skip_list.py
+++ b/Sprint-2/implement_skip_list/skip_list.py
@@ -23,49 +23,49 @@ def _random_level(self):
 
     def insert(self, value):
         update = [None] * (self.MAX_LEVEL + 1)
-        x = self.head
+        current = self.head
 
         # Find the place where the new value should go
-        for i in range(self.level, -1, -1):
-            while x.next[i] and x.next[i].value < value:
-                x = x.next[i]
-            update[i] = x
+        for level in range(self.level, -1, -1):
+            while current.next[level] and current.next[level].value < value:
+                current = current.next[level]
+            update[level] = current
 
-        x0 = x.next[0]
-        if x0 and x0.value == value:
+        next_node = current.next[0]
+        if next_node and next_node.value == value:
             return
 
         node_level = self._random_level()
 
         if node_level > self.level:
-            for i in range(self.level + 1, node_level + 1):
-                update[i] = self.head
+            for level in range(self.level + 1, node_level + 1):
+                update[level] = self.head
             self.level = node_level
 
         new_node = Node(value, node_level)
-        for i in range(node_level + 1):
-            new_node.next[i] = update[i].next[i]
-            update[i].next[i] = new_node
+        for level in range(node_level + 1):
+            new_node.next[level] = update[level].next[level]
+            update[level].next[level] = new_node
     
     # Check if value exists
     def contains(self, value):
-        x = self.head
-        for lvl in range(self.level, -1, -1):
-            while x.next[lvl] and x.next[lvl].value < value:
-                x = x.next[lvl]
+        current = self.head
+        for level in range(self.level, -1, -1):
+            while current.next[level] and current.next[level].value < value:
+                current = current.next[level]
 
-        x = x.next[0]
-        return x is not None and x.value == value
+        candidate = current.next[0]
+        return candidate is not None and candidate.value == value
 
     def __contains__(self, value):
         return self.contains(value)
 
     def to_list(self):
         result = []
-        x = self.head.next[0]
-        while x:
-            result.append(x.value)
-            x = x.next[0]
+        current = self.head.next[0]
+        while current:
+            result.append(current.value)
+            current = current.next[0]
         return result