Given an array of integers nums sorted in ascending order, find the starting and ending position of a given target value.

Given a collection of intervals, merge all overlapping intervals.

Given a m x n matrix, if an element is 0, set its entire row and column to 0. Do it in-place.

Given an array with n objects colored red, white or blue, sort them in-place so that objects of the same color are adjacent, with the colors in the order red, white and blue.

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