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#!/usr/bin/env python3
# Challenge 049
#
# TASK #2
# LRU Cache
# Write a script to demonstrate LRU Cache feature. It should support operations
# get and set. Accept the capacity of the LRU Cache as command line argument.
#
# Definition of LRU: An access to an item is defined as a get or a set operation
# of the item. "Least recently used" item is the one with the oldest access time.
#
# For example:
#
# capacity = 3
# set(1, 3)
# set(2, 5)
# set(3, 7)
#
# Cache at this point:
# [Least recently used] 1,2,3 [most recently used]
#
# get(2) # returns 5
#
# Cache looks like now:
# [Least recently used] 1,3,2 [most recently used]
#
# get(1) # returns 3
#
# Cache looks like now:
# [Least recently used] 3,2,1 [most recently used]
#
# get(4) # returns -1
#
# Cache unchanged:
# [Least recently used] 3,2,1 [most recently used]
#
# set(4, 9)
#
# Cache is full, so pushes out key = 3:
# [Least recently used] 2,1,4 [most recently used]
#
# get(3) # returns -1
class Cache():
capacity = 0
cache = []
def __init__(self, capacity):
self.capacity = capacity
self.cache = []
def __str__(self):
out = ""
for x in self.cache:
out += "(" + str(x[0]) + "=>" + str(x[1]) + ")"
return out
def get(self, k):
for i in range(len(self.cache)):
if self.cache[i][0] == k:
v = self.cache[i][1]
self.cache = self.cache[0:i] + self.cache[i+1:]
self.cache.append([k,v])
return v
return -1
def set(self, k, v):
found = self.get(k)
if found == -1:
self.cache.append([k,v])
while len(self.cache) > self.capacity:
self.cache = self.cache[1:]
else:
self.cache[-1][1] = v
print("Create cache, capacity=>3")
cache = Cache(3)
print("Cache="+str(cache))
print("Set cache:1,3")
cache.set(1, 3)
print("Cache="+str(cache))
print("Set cache:2,5")
cache.set(2, 5)
print("Cache="+str(cache))
print("Set cache:3,7")
cache.set(3, 7)
print("Cache="+str(cache))
print("Get cache 2=>"+str(cache.get(2)))
print("Cache="+str(cache))
print("Get cache 1=>"+str(cache.get(1)))
print("Cache="+str(cache))
print("Get cache 4=>"+str(cache.get(4)))
print("Cache="+str(cache))
print("Set cache:4,9")
cache.set(4, 9)
print("Cache="+str(cache))
print("Get cache 3=>"+str(cache.get(3)))
print("Cache="+str(cache))
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