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Commit35d1c14

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Added tasks 2619-2623
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2619\. Array Prototype Last
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Easy
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Write code that enhances all arrays such that you can call the`array.last()` method on any array and it will return the last element. If there are no elements in the array, it should return`-1`.
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You may assume the array is the output of`JSON.parse`.
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**Example 1:**
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**Input:** nums =[null, {}, 3]
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**Output:** 3
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**Explanation:** Calling nums.last() should return the last element: 3.
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**Example 2:**
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**Input:** nums =[]
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**Output:** -1
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**Explanation:** Because there are no elements, return -1.
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**Constraints:**
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*`0 <= arr.length <= 1000`
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// #Easy #2023_08_31_Time_41_ms_(98.99%)_Space_42_MB_(96.92%)
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declare global{
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interfaceArray<T>{
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last():T|-1;
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}
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}
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Array.prototype.last=function(){//NOSONAR
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returnthis.length!==0 ?this[this.length-1] :-1
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}
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/*
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* const arr = [1, 2, 3];
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* arr.last(); // 3
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*/
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export{}
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2620\. Counter
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Easy
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Given an integer`n`, return a`counter` function. This`counter` function initially returns`n` and then returns 1 more than the previous value every subsequent time it is called (`n`,`n + 1`,`n + 2`, etc).
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**Example 1:**
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**Input:** n = 10["call","call","call"]
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**Output:**[10,11,12]
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**Explanation:**
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counter() = 10 // The first time counter() is called, it returns n.
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counter() = 11 // Returns 1 more than the previous time.
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counter() = 12 // Returns 1 more than the previous time.
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**Example 2:**
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**Input:** n = -2["call","call","call","call","call"]
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**Output:**[-2,-1,0,1,2]
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**Explanation:** counter() initially returns -2. Then increases after each sebsequent call.
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**Constraints:**
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*`-1000<= n <= 1000`
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*`At most 1000 calls to counter() will be made`
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// #Easy #2023_08_31_Time_43_ms_(98.60%)_Space_42.2_MB_(91.27%)
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functioncreateCounter(n:number):()=>number{
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constfun=function(){
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n++
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returnn-1
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}
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returnfun
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}
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/*
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* const counter = createCounter(10)
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* counter() // 10
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* counter() // 11
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* counter() // 12
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*/
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export{createCounter}
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2621\. Sleep
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Easy
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Given a positive integer`millis`, write an asynchronous function that sleeps for`millis` milliseconds. It can resolve any value.
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**Example 1:**
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**Input:** millis = 100
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**Output:** 100
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**Explanation:** It should return a promise that resolves after 100ms. let t = Date.now(); sleep(100).then(() => { console.log(Date.now() - t); // 100 });
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**Example 2:**
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**Input:** millis = 200
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**Output:** 200
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**Explanation:** It should return a promise that resolves after 200ms.
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**Constraints:**
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*`1 <= millis <= 1000`
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// #Easy #2023_08_31_Time_40_ms_(99.59%)_Space_42.3_MB_(77.98%)
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asyncfunctionsleep(millis:number):Promise<void>{
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awaitnewPromise(resolve=>setTimeout(resolve,millis));
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}
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/*
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* let t = Date.now()
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* sleep(100).then(() => console.log(Date.now() - t)) // 100
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*/
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export{sleep}
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2622\. Cache With Time Limit
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Medium
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Write a class that allows getting and setting key-value pairs, however a**time until expiration** is associated with each key.
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The class has three public methods:
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`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.
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`get(key)`: if an un-expired key exists, it should return the associated value. Otherwise it should return`-1`.
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`count()`: returns the count of un-expired keys.
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**Example 1:**
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**Input:**["TimeLimitedCache", "set", "get", "count", "get"][[],[1, 42, 100],[1],[],[1]][0, 0, 50, 50, 150]
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**Output:**[null, false, 42, 1, -1]
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**Explanation:**
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At t=0, the cache is constructed.
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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.
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At t=50, key=1 is requested and the value of 42 is returned.
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At t=50, count() is called and there is one active key in the cache.
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At t=100, key=1 expires.
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At t=150, get(1) is called but -1 is returned because the cache is empty.
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**Example 2:**
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**Input:**["TimeLimitedCache", "set", "set", "get", "get", "get", "count"][[],[1, 42, 50],[1, 50, 100],[1],[1],[1],[]][0, 0, 40, 50, 120, 200, 250]
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**Output:**[null, false, true, 50, 50, -1]
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**Explanation:**
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At t=0, the cache is constructed.
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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.
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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.
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At t=50, get(1) is called which returned 50. At t=120, get(1) is called which returned 50.
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At t=140, key=1 expires. At t=200, get(1) is called but the cache is empty so -1 is returned.
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At t=250, count() returns 0 because the cache is empty.
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**Constraints:**
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* <code>0 <= key <= 10<sup>9</sup></code>
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* <code>0 <= value <= 10<sup>9</sup></code>
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*`0 <= duration <= 1000`
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*`total method calls will not exceed 100`
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// #Medium #2023_08_31_Time_51_ms_(94.82%)_Space_42.2_MB_(94.26%)
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classTimeLimitedCache{
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privatekeyMap:Map<number,any>
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constructor(){
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this.keyMap=newMap<number,any>()
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}
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set(key:number,value:number,duration:number):boolean{
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letexisted:boolean=this.keyMap.has(key)
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if(existed)clearTimeout(this.keyMap.get(key).clearRef)
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this.keyMap.set(key,{
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value,
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clearRef:setTimeout(()=>{
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this.keyMap.delete(key)
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},duration),
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})
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returnexisted
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}
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get(key:number):number{
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returnthis.keyMap.has(key) ?this.keyMap.get(key).value :-1
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}
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count():number{
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returnthis.keyMap.size
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}
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}
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/*
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* Your TimeLimitedCache object will be instantiated and called as such:
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* var obj = new TimeLimitedCache()
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* obj.set(1, 42, 1000); // false
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* obj.get(1) // 42
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* obj.count() // 1
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*/
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export{TimeLimitedCache}
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2623\. Memoize
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Medium
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Given a function`fn`, return a**memoized** version of that function.
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A**memoized**function is a function that will never be called twice with the same inputs. Instead it will return a cached value.
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You can assume there are**3**possible input functions:`sum`**,**`fib`**,**and`factorial`**.**
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*`sum`accepts two integers`a` and`b` and returns`a + b`.
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*`fib`accepts a single integer`n` and returns`1` if`n <= 1` or`fib(n - 1) + fib(n - 2)` otherwise.
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*`factorial` accepts a single integer`n` and returns`1` if`n <= 1` or`factorial(n - 1) * n` otherwise.
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**Example 1:**
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**Input** "sum"["call","call","getCallCount","call","getCallCount"][[2,2],[2,2],[],[1,2],[]]
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**Output:**[4,4,1,3,2]
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**Explanation:**
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const sum = (a, b) => a + b;
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const memoizedSum = memoize(sum);
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memoizedSum(2, 2); // Returns 4. sum() was called as (2, 2) was not seen before.
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memoizedSum(2, 2); // Returns 4. However sum() was not called because the same inputs were seen before.
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// Total call count: 1
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memoizedSum(1, 2); // Returns 3. sum() was called as (1, 2) was not seen before.
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// Total call count: 2
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**Example 2:**
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**Input** "factorial"["call","call","call","getCallCount","call","getCallCount"][[2],[3],[2],[],[3],[]]
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**Output:**[2,6,2,2,6,2]
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**Explanation:**
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const factorial = (n) => (n <= 1) ? 1 : (n\* factorial(n - 1));
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const memoFactorial = memoize(factorial);
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memoFactorial(2); // Returns 2.
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memoFactorial(3); // Returns 6.
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memoFactorial(2); // Returns 2. However factorial was not called because 2 was seen before.
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// Total call count: 2
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memoFactorial(3); // Returns 6. However factorial was not called because 3 was seen before.
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// Total call count: 2
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**Example 3:**
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**Input** "fib"["call","getCallCount"][[5],[]]
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**Output:**[8,1]
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**Explanation:** fib(5) = 8 // Total call count: 1
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**Constraints:**
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* <code>0 <= a, b <= 10<sup>5</sup></code>
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*`1 <= n <= 10`
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* <code>at most 10<sup>5</sup> function calls</code>
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* <code>at most 10<sup>5</sup> attempts to access callCount</code>
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*`input function is sum, fib, or factorial`
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// #Medium #2023_08_31_Time_264_ms_(97.20%)_Space_109.2_MB_(32.97%)
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typeFn=(...params:any)=>any
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functionmemoize(fn:Fn):Fn{
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constmem_args:Map<string,any>=newMap<string,any>()
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returnfunction(...args){
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constargs_str=args.toString()
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if(mem_args.has(args_str)){
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returnmem_args.get(args_str)
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}
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constresult=fn(...args)
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mem_args.set(args_str,result)
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returnresult
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}
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}
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/*
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* let callCount = 0;
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* const memoizedFn = memoize(function (a, b) {
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* callCount += 1;
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* return a + b;
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* })
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* memoizedFn(2, 3) // 5
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* memoizedFn(2, 3) // 5
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* console.log(callCount) // 1
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*/
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export{memoize}
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// tslint:disable:no-magic-numbers
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import'src/main/java/g2601_2700/s2619_array_prototype_last/solution'
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import{expect,test}from'vitest'
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test('last',()=>{
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letnums=[null,{},3].last()
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expect(nums).toEqual(3)
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})
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test('last2',()=>{
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letnums=[].last()
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expect(nums).toEqual(-1)
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})
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// tslint:disable:no-magic-numbers
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import{createCounter}from'src/main/java/g2601_2700/s2620_counter/solution'
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import{expect,test}from'vitest'
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test('createCounter',()=>{
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constcounter=createCounter(10)
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expect(counter()).toEqual(10)
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expect(counter()).toEqual(11)
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expect(counter()).toEqual(12)
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})
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test('createCounter2',()=>{
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constcounter=createCounter(-2)
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expect(counter()).toEqual(-2)
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expect(counter()).toEqual(-1)
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expect(counter()).toEqual(0)
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expect(counter()).toEqual(1)
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expect(counter()).toEqual(2)
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})

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