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# 題目敘述
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.
# 解題思路
# Solution
var TimeLimitedCache = function() { | |
this.cache = new Map(); | |
}; | |
/** | |
* @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) { | |
const val = this.cache.get(key); | |
if(val){ | |
clearTimeout(val.timeout); | |
} | |
const timeout = setTimeout(() => this.cache.delete(key), duration); | |
this.cache.set(key, {value, timeout}); | |
return Boolean(val); | |
}; | |
/** | |
* @param {number} key | |
* @return {number} value associated with key | |
*/ | |
TimeLimitedCache.prototype.get = function(key) { | |
return this.cache.has(key) ? this.cache.get(key).value : -1; | |
}; | |
/** | |
* @return {number} count of non-expired keys | |
*/ | |
TimeLimitedCache.prototype.count = function() { | |
return this.cache.size; | |
}; | |
/** | |
* 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 | |
*/ |
class TimeLimitedCache { | |
cache: Map<any, any>; | |
constructor() { | |
this.cache = new Map(); | |
} | |
set(key: number, value: number, duration: number): boolean { | |
const val: any = this.cache.get(key); | |
if (val) { | |
clearTimeout(val.timeout); | |
} | |
const timeout = setTimeout((): Boolean => this.cache.delete(key), duration); | |
this.cache.set(key, { value, timeout }); | |
return Boolean(val); | |
} | |
get(key: number): number { | |
return this.cache.has(key) ? this.cache.get(key).value : -1; | |
} | |
count(): number { | |
return this.cache.size; | |
} | |
} | |
/** | |
* 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 | |
*/ |
單字
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!! !!
片語 & 搭配詞
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