import java.util.*;

/**
 * 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.
 *
 * Time complexity for set: O(1)
 * Time complexity for get: O(log n)
 * Memory complexity: O(n)
 */

public class TimeMap {
    class TimeNode implements Comparable<TimeNode> {
        int timestamp;
        String value;

        public TimeNode(String value, int timestamp) {
            this.value = value;
            this.timestamp = timestamp;
        }
        @Override
        public int compareTo(TimeNode t) {
            return timestamp - t.timestamp;
        }
    }

    Map<String, ArrayList<TimeNode>> dict;
    public TimeMap() {
        dict = new HashMap<>();
    }

    public void set(String key, String value, int timestamp) {
        dict.putIfAbsent(key, new ArrayList<>());
        dict.get(key).add(new TimeNode(value, timestamp));
    }

    public String get(String key, int timestamp) {
        if (dict.containsKey(key)) {
            List<TimeNode> list = dict.get(key);
            int index = Collections.binarySearch(list, new TimeNode("", timestamp));
            if (index != -1) {
                if (index >= 0) return list.get(index).value;
                else return list.get(-(index + 2)).value;
            }
        }
        return "";
    }
}
