## Copy List with Random Pointer

Title: Copy List with Random Pointer Source: leetcode.com A linked list is given such that each node contains an additional random pointer which could point to any node in the list or null. Return a deep copy of the list. Java solution Java /* https://leetcode.com/problems/copy-list-with-random-pointer/ */ import java.util.HashMap; public class CopyListWithRandomPointers { public RandomListNode copyRandomList(RandomListNode ...

## Contains Duplicate III

Title: Contains Duplicate III Source: leetcode.com Given an array of integers, find out whether there are two distinct indices i and j in the array such that the difference between nums[i] and nums[j] is at most t and the difference between i and j is at most k. Java solution Java /*https://leetcode.com/problems/contains-duplicate-iii/*/ public class ContainsDuplicateIII ...

## Contains Duplicate II

Title: Contains Duplicate II Source: leetcode.com 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 difference between i and j is at most k. Java solution Java /* https://leetcode.com/problems/contains-duplicate-ii/ */ import java.util.HashMap; public class ...

## Contains Duplicate

Title: Contains Duplicate Source: leetcode.com 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. Java solution Java /* https://leetcode.com/problems/contains-duplicate/ */ import java.util.HashSet; public class ContainsDuplicate { public ...

## Container With Most Water

Title: Container With Most Water Source: leetcode.com 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 line i is at (i, ai) and (i, 0). Find two lines, which together with x-axis forms a container, such ...

## Clone Graph

Title: Clone Graph Source: leetcode.com Clone an undirected graph. Each node in the graph contains a label and a list of its neighbors. Nodes are labeled uniquely. Java solution Java /* https://leetcode.com/problems/clone-graph/ */ import java.util.HashMap; import java.util.List; import java.util.ArrayList; public class CloneGraph { public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) { if(node==null) return null; HashMap<Integer, UndirectedGraphNode> visited = ...

## Climbing Stairs

Title: Climbing Stairs Source: leetcode.com You are climbing a stair case. It takes n steps to reach to the top. Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top? Java solution Java /* https://leetcode.com/problems/climbing-stairs/ */ import java.util.HashSet; class ClimbStairs { HashSet set = ...

## Binary Tree Paths

Title: Binary Tree Paths Source: leetcode.com Given a binary tree, return all root-to-leaf paths. For example, given the following binary tree: 1 / \ 2 3 \ 5 12345    1 /   \2     3 \  5 All root-to-leaf paths are: ["1->2->5", "1->3"] 1 ["1->2->5", "1->3"] Java solution Java /* https://leetcode.com/problems/binary-tree-paths/ */ import java.util.List; import java.util.ArrayList; public ...