Given an array of integers, return indices of the two numbers such that they add up to a specific target.

Given two strings s and t, return true if t is an anagram of s, and false otherwise.

Given an integer array nums and an integer k, return true if there are two distinct indices i and j in the array such that nums[i] == nums[j] and abs(i - j) <= k.

Find all unique quadruplets in the array which gives the sum of target.

Given two sorted arrays nums1 and nums2 of size m and n respectively, return the median of the two sorted arrays. The overall run time complexity should be O(log (m+n)).

Given a non-empty array of integers nums, every element appears twice except for one. Find that single one. You must implement a solution with linear runtime complexity and use only constant extra space.

You are climbing a staircase. It takes n steps to reach the top. Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?

Given a string s, return the longest palindromic substring in s.

Given the head of a singly linked list, reverse the list, and return the reversed list.

You are given the heads of two sorted linked lists list1 and list2. Merge the two lists into one sorted list. The list should be made by splicing together the nodes of the first two lists.

Given a signed 32-bit integer x, return x with its digits reversed. If reversing x causes the value to go outside the signed 32-bit integer range, return 0.

Given a string s, find the length of the longest substring without repeating characters.

Given the root of a binary tree, determine if it is a valid binary search tree (BST).

Find all unique triplets in the array which gives the sum of zero.