Time Based Key-Value Store

Description

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.

Solution(javascript)

/** Map + Binary Search
 * Initialize your data structure here.
 */
const TimeMap = function () {
  this.map = {}
}

/**
 * @param {string} key
 * @param {string} value
 * @param {number} timestamp
 * @return {void}
 */
TimeMap.prototype.set = function (key, value, timestamp) {
  if (this.map[key]) {
    this.map[key].push([timestamp, value])
  } else {
    this.map[key] = [[timestamp, value]]
  }
}

/**
 * @param {string} key
 * @param {number} timestamp
 * @return {string}
 */
TimeMap.prototype.get = function (key, timestamp) {
  if (!this.map[key]) {
    return ''
  }
  let low = 0
  let high = this.map[key].length - 1
  let result = ''
  while (low <= high) {
    const middle = Math.floor((low + high) / 2)
    const currentStamp = this.map[key][middle][0]
    const currentValue = this.map[key][middle][1]
    if (currentStamp === timestamp) {
      result = currentValue
      break
    } else if (currentStamp < timestamp) {
      result = currentValue
      low = middle + 1
    } else {
      high = middle - 1
    }
  }
  return result
}

/**
 * Your TimeMap object will be instantiated and called as such:
 * var obj = new TimeMap()
 * obj.set(key,value,timestamp)
 * var param_2 = obj.get(key,timestamp)
 */
// @lc code=end