981. Time Based Key-Value Store

Medium

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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"]


class TimeMap {
public:
    /** Initialize your data structure here. */
    TimeMap() {
        
    }
    
    void set(string key, string value, int timestamp) {
        Map[key][timestamp] = value;
    }
    
    string get(string key, int timestamp) {
        string Result = "";
        if(Map.count(key) == 0){
            return Result;
        }
        if(Map[key].count(timestamp) != 0){
            Result = Map[key][timestamp];
            return Result;
        }
        map<int,string>::reverse_iterator it = Map[key].rbegin();
        for(it;it != Map[key].rend();it++){
            if(it->first > timestamp){
                continue;
            }
            Result = it->second;
            return Result;
        }
        return Result;
    }
    private:
        unordered_map<string,map<int,string>> Map;
};

/**
 * Your TimeMap object will be instantiated and called as such:
 * TimeMap* obj = new TimeMap();
 * obj->set(key,value,timestamp);
 * string param_2 = obj->get(key,timestamp);
 */