146.lru-cache.python3.py

#
# [146] LRU Cache
#
# https://leetcode.com/problems/lru-cache/description/
#
# algorithms
# Hard (21.19%)
# Total Accepted:    213.9K
# Total Submissions: 981.7K
# Testcase Example:  '["LRUCache","put","put","get","put","get","put","get","get","get"]\n[[2],[1,1],[2,2],[1],[3,3],[2],[4,4],[1],[3],[4]]'
#
# 
# Design and implement a data structure for Least Recently Used (LRU) cache. It
# should support the following operations: get and put.
# 
# 
# 
# get(key) - Get the value (will always be positive) of the key if the key
# exists in the cache, otherwise return -1.
# put(key, value) - Set or insert the value if the key is not already present.
# When the cache reached its capacity, it should invalidate the least recently
# used item before inserting a new item.
# 
# 
# Follow up:
# Could you do both operations in O(1) time complexity?
# 
# Example:
# 
# LRUCache cache = new LRUCache( 2 /* capacity */ );
# 
# cache.put(1, 1);
# cache.put(2, 2);
# cache.get(1);       // returns 1
# cache.put(3, 3);    // evicts key 2
# cache.get(2);       // returns -1 (not found)
# cache.put(4, 4);    // evicts key 1
# cache.get(1);       // returns -1 (not found)
# cache.get(3);       // returns 3
# cache.get(4);       // returns 4
# 
# 
#
from collections import OrderedDict


class LRUCache:

    def __init__(self, capacity):
        """
        :type capacity: int
        """
        self._cap = capacity
        self._data = OrderedDict()

    def get(self, key):
        """
        :type key: int
        :rtype: int
        """
        res =  self._data.get(key, -1)
        if res != -1:
            self._data.move_to_end(key)
        return res

    def put(self, key, value):
        """
        :type key: int
        :type value: int
        :rtype: void
        """
        if key not in self._data:
            self._data[key] = value
        else:
            self._data[key] = value
            self._data.move_to_end(key)

        while len(self._data) > self._cap:
            self._data.popitem(last=False)
        

        


# Your LRUCache object will be instantiated and called as such:
# obj = LRUCache(capacity)
# param_1 = obj.get(key)
# obj.put(key,value)