LRU cache design

Question

Least Recently Used (LRU) Cache is to discard the least recently used items first How do you design and implement such a cache class? The design requirements are as follows:

Answer 1

LRU Page Replacement Technique:

When a page is referenced, the required page may be in the cache.

If in the cache: we need to bring it to the front of the cache queue.

If NOT in the cache: we bring that in cache. In simple words, we add a new page to the front of the cache queue. If the cache is full, i.e. all the frames are full, we remove a page from the rear of cache queue, and add the new page to the front of cache queue.

# Cache Size
csize = int(input())

# Sequence of pages 
pages = list(map(int,input().split()))

# Take a cache list
cache=[]

# Keep track of number of elements in cache
n=0

# Count Page Fault
fault=0

for page in pages:
    # If page exists in cache
    if page in cache:
        # Move the page to front as it is most recent page
        # First remove from cache and then append at front
        cache.remove(page)
        cache.append(page)
    else:
        # Cache is full
        if(n==csize):
            # Remove the least recent page 
            cache.pop(0)
        else:
            # Increment element count in cache
            n=n+1

        # Page not exist in cache => Page Fault
        fault += 1
        cache.append(page)

print("Page Fault:",fault)

Input/Output

Input:
3
1 2 3 4 1 2 5 1 2 3 4 5

Output:
Page Fault: 10