Algorithm
Problem Name: 981. Time Based Key-Value Store
Problem Link: https://leetcode.com/problems/time-based-key-value-store/
Design a time-based key-value data structure that can store multiple values for the same key at different time stamps and retrieve the key's value at a certain timestamp.
Implement the TimeMap class:
TimeMap()Initializes the object of the data structure.void set(String key, String value, int timestamp)Stores the keykeywith the valuevalueat the given timetimestamp.String get(String key, int timestamp)Returns a value such thatsetwas called previously, withtimestamp_prev <= timestamp. If there are multiple such values, it returns the value associated with the largesttimestamp_prev. If there are no values, it returns"".
Example 1:
Input
["TimeMap", "set", "get", "get", "set", "get", "get"]
[[], ["foo", "bar", 1], ["foo", 1], ["foo", 3], ["foo", "bar2", 4], ["foo", 4], ["foo", 5]]
Output
[null, null, "bar", "bar", null, "bar2", "bar2"]
Explanation
TimeMap timeMap = new TimeMap();
timeMap.set("foo", "bar", 1); // store the key "foo" and value "bar" along with timestamp = 1.
timeMap.get("foo", 1); // return "bar"
timeMap.get("foo", 3); // return "bar", since there is no value corresponding to foo at timestamp 3 and timestamp 2, then the only value is at timestamp 1 is "bar".
timeMap.set("foo", "bar2", 4); // store the key "foo" and value "bar2" along with timestamp = 4.
timeMap.get("foo", 4); // return "bar2"
timeMap.get("foo", 5); // return "bar2"
Constraints:
1 <= key.length, value.length <= 100keyandvalueconsist of lowercase English letters and digits.1 <= timestamp <= 107- All the timestamps
timestampofsetare strictly increasing. - At most
2 * 105calls will be made tosetandget.
Code Examples
#1 Code Example with Java Programming
Code -
Java Programming
class TimeMap {
private Map();
}
public void set(String key, String value, int timestamp) {
this.map.computeIfAbsent(key, k -> new ArrayList<>()).add(new TimeStampValuePair(timestamp, value));
}
public String get(String key, int timestamp) {
if (!this.map.containsKey(key)) {
return "";
}
List < TimeStampValuePair> pairs = this.map.get(key);
int left = 0;
int right = pairs.size() - 1;
int maxIdx = -1;
while (left < = right) {
int mid = (left + right) / 2;
if (pairs.get(mid).timestamp <= timestamp) {
maxIdx = mid;
left = mid + 1;
} else {
right = mid - 1;
}
}
return maxIdx == -1 ? "" : pairs.get(maxIdx).value;
}
private class TimeStampValuePair {
int timestamp;
String value;
public TimeStampValuePair(int timestamp, String value) {
this.timestamp = timestamp;
this.value = value;
}
}
}
Input
["TimeMap", "set", "get", "get", "set", "get", "get"]
[[], ["foo", "bar", 1], ["foo", 1], ["foo", 3], ["foo", "bar2", 4], ["foo", 4], ["foo", 5]]
Output
[null, null, "bar", "bar", null, "bar2", "bar2"]
#2 Code Example with Javascript Programming
Code -
Javascript Programming
const TimeMap = function() {
this.hash = {}
};
TimeMap.prototype.set = function(key, value, timestamp) {
if(this.hash[key] == null) this.hash[key] = []
this.hash[key].push([value, timestamp])
};
TimeMap.prototype.get = function(key, timestamp) {
if(this.hash[key] == null) return ''
const arr = this.hash[key]
let l = 0, r = arr.length - 1;
while(l <= r) {
const pick = Math.floor((l + r) / 2);
if (arr[pick][1] < timestamp> {
l = pick + 1;
} else if (arr[pick][1] > timestamp) {
r = pick - 1
} else {
return arr[pick][0];
}
}
return arr[r]?.[0] || ''
};
Input
["TimeMap", "set", "get", "get", "set", "get", "get"]
[[], ["foo", "bar", 1], ["foo", 1], ["foo", 3], ["foo", "bar2", 4], ["foo", 4], ["foo", 5]]
Output
[null, null, "bar", "bar", null, "bar2", "bar2"]
#3 Code Example with Python Programming
Code -
Python Programming
class TimeMap:
def __init__(self):
self.times = collections.defaultdict(list)
self.values = collections.defaultdict(list)
def set(self, key: str, value: str, timestamp: int) -> None:
self.times[key].append(timestamp)
self.values[key].append(value)
def get(self, key: str, timestamp: int) -> str:
i = bisect.bisect(self.times[key], timestamp)
return self.values[key][i - 1] if i else ''
Input
["TimeMap", "set", "get", "get", "set", "get", "get"]
[[], ["foo", "bar", 1], ["foo", 1], ["foo", 3], ["foo", "bar2", 4], ["foo", 4], ["foo", 5]]
Output
[null, null, "bar", "bar", null, "bar2", "bar2"]
#4 Code Example with C# Programming
Code -
C# Programming
using System.Collections.Generic;
namespace LeetCode
{
public class _0981_TimeBasedKeyValueStore
{
private readonly IDictionary < string, SortedList<int, string>> map;
/** Initialize your data structure here. */
public _0981_TimeBasedKeyValueStore()
{
map = new Dictionary < string, SortedList<int, string>>();
}
public void Set(string key, string value, int timestamp)
{
if (!map.ContainsKey(key))
map.Add(key, new SortedList < int, string>());
map[key].Add(timestamp, value);
}
public string Get(string key, int timestamp)
{
if (!map.ContainsKey(key)) return string.Empty;
var list = map[key];
for (var i = list.Count - 1; i >= 0; i--)
if (list.Keys[i] < = timestamp)
return list.Values[i];
return string.Empty;
}
}
}
Input
["TimeMap", "set", "get", "get", "set", "get", "get"]
[[], ["foo", "bar", 1], ["foo", 1], ["foo", 3], ["foo", "bar2", 4], ["foo", 4], ["foo", 5]]
Output
[null, null, "bar", "bar", null, "bar2", "bar2"]