Create a timebased key-value store class TimeMap
, that supports two operations.
1. set(string key, string value, int timestamp)
- Stores the
key
andvalue
, along with the giventimestamp
.
2. get(string key, int timestamp)
- Returns a value such that
set(key, value, timestamp_prev)
was called previously, withtimestamp_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 allTimeMap.set
operations are strictly increasing. 1 <= timestamp <= 10^7
TimeMap.set
andTimeMap.get
functions will be called a total of120000
times (combined) per test case.
Solution: HashTable + Map
C++
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// Author: Huahua, running time: 200 ms class TimeMap { public: /** Initialize your data structure here. */ TimeMap() {} void set(string key, string value, int timestamp) { s_[key].emplace(timestamp, std::move(value)); } string get(string key, int timestamp) { auto m = s_.find(key); if (m == s_.end()) return ""; auto it = m->second.upper_bound(timestamp); if (it == begin(m->second)) return ""; return prev(it)->second; } private: unordered_map<string, map<int, string>> s_; }; |
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