Egbert Lin's Blog

19. Remove Nth Node From End of List

Question:

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

Follow up: Could you do this in one pass?

15. 3Sum

Question:

Given an array nums of n integers, are there elements a, b, c in nums such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero.

Notice that the solution set must not contain duplicate triplets.

11. Container With Most Water

Question:

Given n non-negative integers a1, a2, ..., an , where each represents a point at coordinate (i, ai). n vertical lines are drawn such that the two endpoints of the line i is at (i, ai) and (i, 0). Find two lines, which, together with the x-axis forms a container, such that the container contains the most water.

5. Longest Palindromic Substring

Question:

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

Example:

Input: s = "babad"
Output: "bab"
Note: "aba" is also a valid answer.

3. Longest Substring Without Repeating Characters

Question:

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

Example:

Input: s = "abcabcbb"
Output: 3
Explanation: The answer is "abc", with the length of 3.

225. Implement Stack using Queues

Question:

Implement a last in first out (LIFO) stack using only two queues. The implemented stack should support all the functions of a normal queue (push, top, pop, and empty).

219. Contains Duplicate II

Question:

Given an array of integers and an integer k, find out whether there are two distinct indices i and j in the array such that nums[i] = nums[j] and the absolute difference between i and j is at most k.

217. Contains Duplicate

Question:

Given an array of integers, find if the array contains any duplicates.

Your function should return true if any value appears at least twice in the array, and it should return false if every element is distinct.

206. Reverse Linked List

Question:

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

205. Isomorphic Strings

Question:

Given two strings s and t, determine if they are isomorphic.

Two strings s and t are isomorphic if the characters in s can be replaced to get t.

All occurrences of a character must be replaced with another character while preserving the order of characters. No two characters may map to the same character, but a character may map to itself.