Leetcode Solutions

Here are solutions (hopefully) to some of the problems on Leetcode, which is a collection of programming challenges.

Problems

Array Partition I
- Given an array of 2n integers, your task is to group these integers into n pairs of integer, say (a1, b1), (a2, b2), ..., (an, bn) which makes sum of min(ai, bi) for all i from 1 to n as large as possible.
Invert Binary Tree
Longest Substring Without Repeating Characters
- Given a string, find the length of the longest substring without repeating characters.
- CodeReview discussion
Maximum Depth of Binary Tree
Single Number
- Given an array of integers, every element appears twice except for one. Find that single one.
Two Sum
- Given an array of integers, return indices of the two numbers such that they add up to a specific target. You may assume that each input would have exactly one solution, and you may not use the same element twice.
Linked List Addition
- You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list. You may assume the two numbers do not contain any leading zero, except the number 0 itself.
Product of Array Except Self
- Given an array of n integers where n > 1, nums, return an array output such that output[i] is equal to the product of all the elements of nums except nums[i].
- Solve it without division and in O(n).
- For example, given [1, 2, 3, 4] return [24, 12, 8, 6].