LeetCode [981] Time Based Key-Value Store

981. Time Based Key-Value Store

Medium

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:

1. All key/value strings are lowercase.
2. All key/value strings have length in the range [1, 100]
3. The timestamps for all TimeMap.set operations are strictly increasing.
4. 1 <= timestamp <= 10^7
5. TimeMap.set and TimeMap.get functions will be called a total of 120000 times (combined) per test case.

//C++
class TimeMap {
    map<string, vector<pair<int, string>>> mp;
    void insert(vector<pair<int, string>>& vec, int ts, string value){
        int n = vec.size(), l = 0, r = n-1;
        auto it = vec.begin();
        int m;//the first timestamp > st, if not exist m = n
        while(l<=r){
            m = (l+r)/2;
            if(m<0||m>=n) break;
            if((it+m)->first>ts && (m>0 || (it+m-1)->first<=ts)) break;
            if((it+m)->first>ts) r = m-1;
            else l = m+1;
        }

        if(!(m>=0 && m<n && (it+m)->first>ts && (m>0 || (it+m-1)->first<=ts))) m = n;
        vec.insert(it+m, pair<int, string>(ts, value));
    }

    string search(vector<pair<int, string>>& vec, int ts){
        int n = vec.size(), l = 0, r = n-1;
        int m;//the last (it+m)->first<=ts;
        auto it = vec.begin();
        while(l<=r)
        {
            m  = (l+r)/2;
            if(m<0||m>=n) break;
            if((it+m)->first<=ts && (m==n-1 || (it+m+1)->first>ts)) break;
            if((it+m)->first<=ts) l = m+1;
            else r = m-1;
        }
        if(m>=0 && m<n && (it+m)->first<=ts && (m==n-1 || (it+m+1)->first>ts)) return (it+m)->second;
        return "";
    }
public:
    /** Initialize your data structure here. */
    TimeMap() {
        
    }
    
    void set(string key, string value, int timestamp) {
        if(mp.count(key)==0) mp[key] = vector<pair<int, string>>();
        insert(mp[key], timestamp, value);
    }
    
    string get(string key, int timestamp) {
        return search(mp[key], timestamp);
    }
};

//Java
class TimeMap {
    Map<String, TreeMap<Integer, String>> map;

    /** Initialize your data structure here. */
    public TimeMap() {
        map = new HashMap<>();
    }
    
    public void set(String key, String value, int timestamp) {
        map.computeIfAbsent(key, k -> new TreeMap<Integer, String>()).put(timestamp, value);
    }
    
    public String get(String key, int timestamp) {
        if(!map.containsKey(key)) return "";
        Integer floor = map.get(key).floorKey(timestamp);//key<=timestamp;
        if(floor == null) return "";
        return map.get(key).get(floor);
    }
}

/**
 * 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);
 */