Time Based Key-Value Store — HashMap + Binary Search

# Python
from collections import defaultdict
import bisect
class TimeMap:
    def __init__(self): self.store = defaultdict(list)
    def set(self, key, value, timestamp):
        self.store[key].append((timestamp, value))
    def get(self, key, timestamp):
        lst = self.store[key]
        i = bisect.bisect_right(lst, (timestamp, chr(127))) - 1
        return lst[i][1] if i >= 0 else ""

// Java
class TimeMap {
    Map<String, List<int[]>> map = new HashMap<>();
    Map<String, List<String>> vals = new HashMap<>();
    public void set(String key, String value, int timestamp) {
        map.computeIfAbsent(key, k -> new ArrayList<>()).add(new int[]{timestamp});
        vals.computeIfAbsent(key, k -> new ArrayList<>()).add(value);
    }
    public String get(String key, int timestamp) {
        if (!map.containsKey(key)) return "";
        List<int[]> times = map.get(key);
        int lo=0, hi=times.size()-1, idx=-1;
        while (lo<=hi) {
            int mid=(lo+hi)/2;
            if (times.get(mid)[0]<=timestamp) { idx=mid; lo=mid+1; }
            else hi=mid-1;
        }
        return idx==-1 ? "" : vals.get(key).get(idx);
    }
}

// C++
class TimeMap {
    unordered_map<string, vector<pair<int,string>>> store;
public:
    void set(string key, string value, int timestamp) {
        store[key].push_back({timestamp, value});
    }
    string get(string key, int timestamp) {
        if (!store.count(key)) return "";
        auto& v = store[key];
        auto it = upper_bound(v.begin(), v.end(), make_pair(timestamp, string(200,'z')));
        return it == v.begin() ? "" : prev(it)->second;
    }
};