Engineering

Given an integer array nums and an integer val, remove all occurrences of val in nums in-place. The relative order of the elements may be changed.

Implement strStr(). Return the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.

An n-bit gray code sequence is a sequence of 2n integers where

Given two integers n and k, return all possible combinations of k numbers out of the range [1, n].

Given a collection of numbers, nums, that might contain duplicates, return all possible unique permutations in any order.

A robot is located at the top-left corner of a m x n grid (marked 'Start' in the diagram below).

Given an array nums of distinct integers, return all the possible permutations. You can return the answer in any order.

Given the head of a linked list, remove the nth node from the end of the list and return its head.

Given a string containing digits from 2-9 inclusive, return all possible letter combinations that the number could represent. Return the answer in any order.