981 Time Based Key-Value Store.py

#!/usr/bin/python3
"""
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.
2. 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:

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


class TimeMap:

    def __init__(self):
        """
        Initialize your data structure here.
        Looks like Cassandra
        Heap? Largest timestamp_prev <= timestamp
        BST
        Bineary search
        """
        self.m = defaultdict(list)

    def set(self, key: str, value: str, timestamp: int) -> None:
        n = (timestamp, value)
        bisect.insort(self.m[key], n)

    def get(self, key: str, timestamp: int) -> str:
        if key not in self.m:
            return ""

        # find the largest v, s.t. v <= t
        lst = self.m[key]
        i = bisect.bisect(lst, (timestamp, ""))
        if i < len(lst) and lst[i][0] == timestamp:
            return lst[i][1]
        i -= 1
        if i >= 0:
            return lst[i][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)