# 981. Time Based Key-Value Store

#### Medium

***

Design a time-based key-value data structure that can store multiple values for the same key at different time stamps and retrieve the key's value at a certain timestamp.

Implement the `TimeMap` class:

* `TimeMap()` Initializes the object of the data structure.
* `void set(String key, String value, int timestamp)` Stores the key `key` with the value `value` at the given time `timestamp`.
* `String get(String key, int timestamp)` Returns a value such that `set` was called previously, with `timestamp_prev <= timestamp`. If there are multiple such values, it returns the value associated with the largest `timestamp_prev`. If there are no values, it returns `""`.

&#x20;

**Example 1:**

<pre><code>Input
["TimeMap", "set", "get", "get", "set", "get", "get"]
[[], ["foo", "bar", 1], ["foo", 1], ["foo", 3], ["foo", "bar2", 4], ["foo", 4], ["foo", 5]]
<strong>Output
</strong>[null, null, "bar", "bar", null, "bar2", "bar2"]
<strong>Explanation
</strong>TimeMap timeMap = new TimeMap();
timeMap.set("foo", "bar", 1);  // store the key "foo" and value "bar" along with timestamp = 1.
timeMap.get("foo", 1);         // return "bar"
timeMap.get("foo", 3);         // return "bar", since there is no value corresponding to foo at timestamp 3 and timestamp 2, then the only value is at timestamp 1 is "bar".
timeMap.set("foo", "bar2", 4); // store the key "foo" and value "bar2" along with timestamp = 4.
timeMap.get("foo", 4);         // return "bar2"
timeMap.get("foo", 5);         // return "bar2"
</code></pre>

&#x20;

**Constraints:**

* `1 <= key.length, value.length <= 100`
* `key` and `value` consist of lowercase English letters and digits.
* `1 <= timestamp <= 107`
* All the timestamps `timestamp` of `set` are strictly increasing.
* At most `2 * 105` calls will be made to `set` and `get`.

```python
class TimeMap:
    def __init__(self):
        self.times = collections.defaultdict(list)
        self.values = collections.defaultdict(list)

    def set(self, key: str, value: str, timestamp: int) -> None:
        self.times[key].append(timestamp)
        self.values[key].append(value)

    def get(self, key: str, timestamp: int) -> str:
        i = bisect.bisect(self.times[key], timestamp)
        return self.values[key][i - 1] if i else ''
```