Today, we will solve the 7th problem of the March LeetCoding Challenge.

Design a HashMap without using any built-in hash table libraries.

To be specific, your design should include these functions:

`put(key, value)`

: Insert a (key, value) pair into the HashMap. If the value already exists in the HashMap, update the value.`get(key)`

: Returns the value to which the specified key is mapped, or -1 if this map contains no mapping for the key.`remove(key)`

: Remove the mapping for the value key if this map contains the mapping for the key.

**Example:**

`MyHashMap hashMap = new MyHashMap();`

hashMap.put(1, 1)…

I know it is hard to get a vaccine slot. I have been trying to get a slot for the last two weeks; still have not got it. Therefore I decided to make a python script that will notify me about the vaccination slots.

For this, we will use the APIs provided by our Indian Government and scrap the page. If you try to do a lot of requests to the server, your IP address may be blocked. BEWARE!!!!!!!!!!!

**Web scraping** is the process of using bots to extract content and data from a website.

Today is May the 4th. Happy Star Wars Day everyone.

Let’s solve some Leetcode problems today. Today we will solve the 4th problem of the May LeetCoding Challenge 2021.

`nums`

with `n`

integers, your task is to check if it could become non-decreasing by modifying We define an array is non-decreasing if `nums[i] <= nums[i + 1]`

holds for every `i`

(**0-based**) such that (`0 <= i <= n - 2`

).

**Example 1:**

**Input:** nums = [4,2,3]

**Output:** true

**Explanation:** You could modify the first 4 to 1 to get a non-decreasing array.

**Example 2:**

**Input:** nums = [4,2,1]

**Output:** false

**Explanation:** You can't get a non-decreasing array by modify at most one element.

We are…

Today, we will solve the 3rd problem of the May LeetCoding Challenge 2021.

Given an array `nums`

. We define a running sum of an array as `runningSum[i] = sum(nums[0]…nums[i])`

.

Return the running sum of `nums`

.

**Example 1:**

**Input:** nums = [1,2,3,4]

**Output:** [1,3,6,10]

**Explanation:** Running sum is obtained as follows: [1, 1+2, 1+2+3, 1+2+3+4].

**Example 2:**

**Input:** nums = [1,1,1,1,1]

**Output:** [1,2,3,4,5]

**Explanation:** Running sum is obtained as follows: [1, 1+1, 1+1+1, 1+1+1+1, 1+1+1+1+1].

**Example 3:**

**Input:** nums = [3,1,2,10,1]

**Output:** [3,4,6,16,17]

This is a pretty easy problem. Here we have to find the running sum of an array. That…

Today, we will solve the 6th problem of the April LeetCoding Challenge 2021.

You have an array `arr`

of length `n`

where `arr[i] = (2 * i) + 1`

for all valid values of `i`

(i.e. `0 <= i < n`

).

In one operation, you can select two indices `x`

and `y`

where `0 <= x, y < n`

and subtract `1`

from `arr[x]`

and add `1`

to `arr[y]`

(i.e. perform `arr[x] -=1 `

and `arr[y] += 1`

). The goal is to make all the elements of the array **equal**. …

From today, we will start doing the April LeetCoding Challenge. You can check the March LeetCoding Challenge problems on my profile.

Given the `head`

of a singly linked list, return `true`

if it is a palindrome.

**Example 1:**

Today we will solve the problem named Authentication Manager.

There is an authentication system that works with authentication tokens. For each session, the user will receive a new authentication token that will expire `timeToLive`

seconds after the `currentTime`

. If the token is renewed, the expiry time will be **extended** to expire `timeToLive`

seconds after the (potentially different) `currentTime`

.

Implement the `AuthenticationManager`

class:

`AuthenticationManager(int timeToLive)`

constructs the`AuthenticationManager`

and sets the`timeToLive`

.`generate(string tokenId, int currentTime)`

generates a new token with the given`tokenId`

at the given`currentTime`

in seconds.`renew(string tokenId, int currentTime)`

renews the**unexpired**token with the given…

Today, we will solve the 19th problem of the March LeetCoding Challenge.

There are `N`

rooms and you start in room `0`

. Each room has a distinct number in `0, 1, 2, ..., N-1`

, and each room may have some keys to access the next room.

Formally, each room `i`

has a list of keys `rooms[i]`

, and each key `rooms[i][j]`

is an integer in `[0, 1, ..., N-1]`

where `N = rooms.length`

. A key `rooms[i][j] = v`

opens the room with number `v`

.

Initially, all the rooms start locked (except for room `0`

).

You can walk back and forth between…

Today, we will solve the 18th problem of the March LeetCoding Challenge.

Given an integer array `nums`

, return *the length of the longest *** wiggle sequence**.

A **wiggle sequence** is a sequence where the differences between successive numbers strictly alternate between positive and negative. The first difference (if one exists) may be either positive or negative. A sequence with fewer than two elements is trivially a wiggle sequence.

- For example,
`[1, 7, 4, 9, 2, 5]`

is a**wiggle sequence**because the differences`(6, -3, 5, -7, 3)`

are alternately positive and negative. - In contrast,
`[1, 4, 7, 2, 5]`

and…

Today, we will solve the 15th problem of the March LeetCoding Challenge.

TinyURL is a URL shortening service where you enter a URL such as `https://leetcode.com/problems/design-tinyurl`

and it returns a short URL such as `http://tinyurl.com/4e9iAk`

.

Design the `encode`

and `decode`

methods for the TinyURL service. There is no restriction on how your encode/decode algorithm should work. You just need to ensure that a URL can be encoded to a tiny URL and the tiny URL can be decoded to the original URL.

In this problem, we have to design an URL shortening service to encode and decode URLs. Therefore for…

Tech-enthusiastic . Connect me — https://twitter.com/sourav__saikia