[Class] Cache With Time Limit

https://leetcode.com/problems/cache-with-time-limit/description/

Cache With Time Limit - LeetCode

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: 
["TimeLimitedCache", "set", "get", "count", "get"]
[[], [1, 42, 100], [1], [], [1]]
[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: 
["TimeLimitedCache", "set", "set", "get", "get", "get", "count"]
[[], [1, 42, 50], [1, 50, 100], [1], [1], [1], []]
[0, 0, 40, 50, 120, 200, 250]
Output: [null, false, true, 50, 50, -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 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 <= 109
• 0 <= value <= 109
• 0 <= duration <= 1000
• total method calls will not exceed 100

 

solution

var TimeLimitedCache = function() {
    this.caches = {};
    this.timeouts = {};
};

/** 
 * @param {number} key
 * @param {number} value
 * @param {number} duration time until expiration in ms
 * @return {boolean} if un-expired key already existed
 */
TimeLimitedCache.prototype.set = function(key, value, duration) {
    let cacheTime;
    let isExist = false;
    if(this.timeouts[key]) {
        clearTimeout(this.timeouts[key]);
        isExist = true;
    }
    this.caches[key] = value;
    cacheTime = setTimeout(() => {
        delete this.caches[key];
        delete this.timeouts[key];
        clearTimeout(cacheTime);
    }, duration);
    this.timeouts[key] = cacheTime;
    return isExist;
};

/** 
 * @param {number} key
 * @return {number} value associated with key
 */
TimeLimitedCache.prototype.get = function(key) {
    if(this.caches[key] === undefined) {
        return -1;
    } else {
        return this.caches[key];
    }
};

/** 
 * @return {number} count of non-expired keys
 */
TimeLimitedCache.prototype.count = function() {
    return Object.keys(this.caches).length;
};

/**
 * Your TimeLimitedCache object will be instantiated and called as such:
 * var obj = new TimeLimitedCache()
 * obj.set(1, 42, 1000); // false
 * obj.get(1) // 42
 * obj.count() // 1
 */

 

solution2) object를 둘로 나누지 말고 하나로 끝내기

var TimeLimitedCache = function() {
  this.cache = {};
};

/** 
* @param {number} key
* @param {number} value
* @param {number} time until expiration in ms
* @return {boolean} if un-expired key already existed
*/
TimeLimitedCache.prototype.set = function(key, value, duration) {
if (this.cache[key] && this.cache[key].timer) {
  clearTimeout(this.cache[key].timer);
  this.cache[key].value = value;
  this.cache[key].timer = setTimeout(() => {
    this.remove(key);
  }, duration);
  return true;
} else {
  this.cache[key] = {
    value: value,
    timer: setTimeout(() => {
      this.remove(key);
    }, duration)
  };
  return false;
}
};

/** 
* @param {number} key
* @return {number} value associated with key
*/
TimeLimitedCache.prototype.get = function(key) {
  if (this.cache[key] && this.cache[key].timer) {
    return this.cache[key].value;
  } else {
    return -1;
  }
};

/** 
* @return {number} count of non-expired keys
*/
TimeLimitedCache.prototype.count = function() {
  let count = 0;
  for (const key in this.cache) {
    if (this.cache[key].timer) {
      count++;
    }
  }
  return count;
};

TimeLimitedCache.prototype.remove = function(key) {
  delete this.cache[key];
};