# 981. Time Based Key-Value Store 基于时间的键值存储

@TOC

## # 题目描述

Create a timebased key-value store class `TimeMap`, that supports two operations.

1. `set(string key, string value, int timestamp)`
• Stores the `key` and `value`, along with the given timestamp.
1. `get(string key, int timestamp)`
• Returns a value such that set(key, value, timestamp_prev) was called previously, with timestamp_prev <= timestamp.
• If there are multiple such values, it returns the one with the largest timestamp_prev.
• If there are no values, it returns the empty string (`""`).

Example 1:

``````Input: inputs = ["TimeMap","set","get","get","set","get","get"], inputs = [[],["foo","bar",1],["foo",1],["foo",3],["foo","bar2",4],["foo",4],["foo",5]]
Output: [null,null,"bar","bar",null,"bar2","bar2"]
Explanation:
TimeMap kv;
kv.set("foo", "bar", 1); // store the key "foo" and value "bar" along with timestamp = 1
kv.get("foo", 1);  // output "bar"
kv.get("foo", 3); // output "bar" since there is no value corresponding to foo at timestamp 3 and timestamp 2, then the only value is at timestamp 1 ie "bar"
kv.set("foo", "bar2", 4);
kv.get("foo", 4); // output "bar2"
kv.get("foo", 5); //output "bar2"
``````

Example 2:

``````Input: inputs = ["TimeMap","set","set","get","get","get","get","get"], inputs = [[],["love","high",10],["love","low",20],["love",5],["love",10],["love",15],["love",20],["love",25]]
Output: [null,null,null,"","high","high","low","low"]
``````

Note:

1. All key/value strings are lowercase.
2. All key/value strings have length in the range [1, 100]
3. The timestamps for all TimeMap.set operations are strictly increasing.
4. 1 <= timestamp <= 10^7
5. TimeMap.set and TimeMap.get functions will be called a total of 120000 times (combined) per test case.

## # 解题方法

### # 字典

``````class TimeMap(object):

def __init__(self):
"""
"""
self.t_ = collections.defaultdict(list)
self.v_ = collections.defaultdict(list)
self.max_ = collections.defaultdict(int)

def set(self, key, value, timestamp):
"""
:type key: str
:type value: str
:type timestamp: int
:rtype: None
"""
self.t_[key].append(timestamp)
self.v_[key].append(value)
self.max_[key] = max(self.max_[key], timestamp)

def get(self, key, timestamp):
"""
:type key: str
:type timestamp: int
:rtype: str
"""
if key not in self.t_:
return ""
if timestamp >= self.max_[key]:
return self.v_[key][-1]
v = bisect.bisect_right(self.t_[key], timestamp)
if v:
return self.v_[key][v - 1]
return ""

# Your TimeMap object will be instantiated and called as such:
# obj = TimeMap()
# obj.set(key,value,timestamp)
# param_2 = obj.get(key,timestamp)
``````

## # 日期

2019 年 1 月 27 日 —— 这个周赛不太爽