From 4966a50eee23177a7f7fd5577a3fd5f29f7dd96f Mon Sep 17 00:00:00 2001
From: Kshitij <kshitijk@tuta.io>
Date: Wed, 6 Nov 2024 15:25:13 +0530
Subject: [PATCH] Added LRU and optimal code (a7).

---
 .../Assignment-A7 (Page replacement)/LRU.py   | 31 +++++++++++++
 .../Optimal.py                                | 44 +++++++++++++++++++
 2 files changed, 75 insertions(+)
 create mode 100644 Codes/Python version/Assignment-A7 (Page replacement)/LRU.py
 create mode 100644 Codes/Python version/Assignment-A7 (Page replacement)/Optimal.py

diff --git a/Codes/Python version/Assignment-A7 (Page replacement)/LRU.py b/Codes/Python version/Assignment-A7 (Page replacement)/LRU.py
new file mode 100644
index 0000000..5be164e
--- /dev/null
+++ b/Codes/Python version/Assignment-A7 (Page replacement)/LRU.py	
@@ -0,0 +1,31 @@
+class LRU:
+    def __init__(self, capacity):
+        self.capacity = capacity
+        self.cache = {}
+        self.order = []
+
+    def refer(self, page):
+        if page not in self.cache:
+            if len(self.cache) >= self.capacity:
+                lru_page = self.order.pop(0)  # Remove least recently used page
+                del self.cache[lru_page]
+        else:
+            self.order.remove(page)  # Remove page to update its order
+        self.cache[page] = True
+        self.order.append(page)
+
+    def display(self):
+        print("Current Pages in Memory (LRU):", list(self.cache.keys()))
+
+# Simulate LRU
+def lru_simulation(pages, capacity):
+    lru = LRU(capacity)
+    for page in pages:
+        lru.refer(page)
+        lru.display()
+
+# Example Pages and Capacity
+pages = [7, 0, 1, 2, 0, 3, 0, 4]
+capacity = 3
+print("LRU Page Replacement Simulation:")
+lru_simulation(pages, capacity)
diff --git a/Codes/Python version/Assignment-A7 (Page replacement)/Optimal.py b/Codes/Python version/Assignment-A7 (Page replacement)/Optimal.py
new file mode 100644
index 0000000..67c898d
--- /dev/null
+++ b/Codes/Python version/Assignment-A7 (Page replacement)/Optimal.py	
@@ -0,0 +1,44 @@
+class Optimal:
+    def __init__(self, capacity):
+        self.capacity = capacity
+        self.cache = []
+
+    def refer(self, page, future):
+        if page not in self.cache:
+            if len(self.cache) < self.capacity:
+                self.cache.append(page)
+            else:
+                farthest_page = self.find_farthest_page(future)
+                index = self.cache.index(farthest_page)
+                self.cache[index] = page
+
+    def find_farthest_page(self, future):
+        farthest = -1
+        farthest_page = None
+        for page in self.cache:
+            if page not in future:
+                return page
+            try:
+                index = future.index(page)
+                if index > farthest:
+                    farthest = index
+                    farthest_page = page
+            except ValueError:
+                continue
+        return farthest_page
+
+    def display(self):
+        print("Current Pages in Memory (Optimal):", self.cache)
+
+# Simulate Optimal Page Replacement
+def optimal_simulation(pages, capacity):
+    optimal = Optimal(capacity)
+    for i in range(len(pages)):
+        optimal.refer(pages[i], pages[i + 1:])
+        optimal.display()
+
+# Example Pages and Capacity
+pages = [7, 0, 1, 2, 0, 3, 0, 4]
+capacity = 3
+print("\nOptimal Page Replacement Simulation:")
+optimal_simulation(pages, capacity)