2622. Cache With Time Limit
Description
Write a class that allows getting and setting key-value pairs, however a time until expiration is associated with each key.
The class has three public methods:
set(key, value, duration)
: accepts an integer key
, an integer value
, and a duration
in milliseconds. Once the duration
has elapsed, the key should be inaccessible. The method should return true
if the same un-expired key already exists and false
otherwise. Both the value and duration should be overwritten if the key already exists.
get(key)
: if an un-expired key exists, it should return the associated value. Otherwise it should return -1
.
count()
: returns the count of un-expired keys.
Example 1:
Input: actions = ["TimeLimitedCache", "set", "get", "count", "get"] values = [[], [1, 42, 100], [1], [], [1]] timeDelays = [0, 0, 50, 50, 150] Output: [null, false, 42, 1, -1] Explanation: At t=0, the cache is constructed. At t=0, a key-value pair (1: 42) is added with a time limit of 100ms. The value doesn't exist so false is returned. At t=50, key=1 is requested and the value of 42 is returned. At t=50, count() is called and there is one active key in the cache. At t=100, key=1 expires. At t=150, get(1) is called but -1 is returned because the cache is empty.
Example 2:
Input: actions = ["TimeLimitedCache", "set", "set", "get", "get", "get", "count"] values = [[], [1, 42, 50], [1, 50, 100], [1], [1], [1], []] timeDelays = [0, 0, 40, 50, 120, 200, 250] Output: [null, false, true, 50, 50, -1, 0] Explanation: At t=0, the cache is constructed. At t=0, a key-value pair (1: 42) is added with a time limit of 50ms. The value doesn't exist so false is returned. At t=40, a key-value pair (1: 50) is added with a time limit of 100ms. A non-expired value already existed so true is returned and the old value was overwritten. At t=50, get(1) is called which returned 50. At t=120, get(1) is called which returned 50. At t=140, key=1 expires. At t=200, get(1) is called but the cache is empty so -1 is returned. At t=250, count() returns 0 because the cache is empty.
Constraints:
0 <= key, value <= 109
0 <= duration <= 1000
1 <= actions.length <= 100
actions.length === values.length
actions.length === timeDelays.length
0 <= timeDelays[i] <= 1450
actions[i]
is one of "TimeLimitedCache", "set", "get" and "count"- First action is always "TimeLimitedCache" and must be executed immediately, with a 0-millisecond delay
Solutions
Solution 1: Hash Table
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 |
|