class TimeMap {

    // Solution @ Sergey Leschev, Belarusian State University

    // 981. Time Based Key-Value Store
    // 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:
    // All key/value strings are lowercase.
    // All key/value strings have length in the range [1, 100]
    // The timestamps for all TimeMap.set operations are strictly increasing.
    // 1 <= timestamp <= 10^7
    // TimeMap.set and TimeMap.get functions will be called a total of 120000 times (combined) per test case.

    var timestamps = [String: [Int]]()
    var values = [Int: String]()

    
    init() { }

    
    func set(_ key: String, _ value: String, _ timestamp: Int) {
        timestamps[key, default: []].append(timestamp)
        values[timestamp] = value
    }

    
    func get(_ key: String, _ timestamp: Int) -> String {
        guard let arr = timestamps[key] else { return "" }
        guard let first = arr.first, timestamp >= first else { return "" }
        let timekey = binarySearch(arr, timestamp)
        return values[timekey] ?? ""
    }

    
    private func binarySearch(_ nums: [Int], _ target: Int) -> Int {
        var low = 0
        var high = nums.count - 1
        
        while low < high {
            let mid = low + (high - low + 1) / 2
            if target == nums[mid] {
                return target
            } else if target < nums[mid] {
                high = mid - 1
            } else {
                low = mid
            }
        }
        return nums[low]
    }
    
}

/**
 * Your TimeMap object will be instantiated and called as such:
 * let obj = TimeMap()
 * obj.set(key, value, timestamp)
 * let ret_2: String = obj.get(key, timestamp)
 */