Always Beginner

Given an input string, reverse the string word by word. For example, Given s = " the sky is blue ", return " blue is sk...

Evaluate the value of an arithmetic expression in Reverse Polish Notation . Valid operators are + , - , * , / . Each operand may be an i...

Given n points on a 2D plane, find the maximum number of points that lie on the same straight line. We can have statistic about the slope...

Sort a linked list in O(n log n) time using constant space complexity. We can use merge sort to sort linked list. Split the list into sin...

Sort a linked list using insertion sort. Just do it like sorting an array. And for linked list, it is easier to move nodes. Split the link...

Design and implement a data structure for Least Recently Used (LRU) cache. It should support the following operations: get and set . ge...

Given a binary tree, return the postorder traversal of its nodes' values. For example: Given binary tree {1,#,2,3} , 1 \ ...