Given a set of non-overlapping intervals, insert a new interval into the intervals (merge if necessary). You may assume that the intervals were initially sorted according to their start times. Example 1: Given intervals [1,3],[6,9], insert and merge [2,5] in as [1,5],[6,9]. Example 2: Given [1,2],[3,5],[6,7],[8,10],[12,16], insert and merge [4,9] in as [1,2],[3,10],[12,16]. This is because the new interval [4,9] overlaps with [3,5],[6,7],[8,10]. Solution: /** * Definition for an interval. * public class Interval { * int start; * int end; * Interval() { start = 0; end = 0; } * Interval(int s, int e) { start = s; end = e; } * } */ public class Solution { public List<Interval> insert(List<Interval> intervals, Interval newInterval) { List<Interval> ans = new ArrayList<>(); int i=0; while(i<intervals.size() && intervals.get(i).end < newInterval.start) ans.add(intervals.get(i++)); int start = i<intervals.size() ?

Given a string containing just the characters ‘(’ and ‘)’, find the length of the longest valid (well-formed) parentheses substring. For “(()”, the longest valid parentheses substring is “()”, which has length = 2. Another example is “)()())”, where the longest valid parentheses substring is “()()”, which has length = 4. Solution: public class Solution { public int longestValidParentheses(String s) { Stack<Integer> st = new Stack<>(); int ans = 0;

Given an array containing n distinct numbers taken from 0, 1, 2, …, n, find the one that is missing from the array. For example, Given nums = [0, 1, 3] return 2. Note: Your algorithm should run in linear runtime complexity. Could you implement it using only constant extra space complexity? Solution: public class Solution { public int missingNumber(int[] nums) { int sum = 0; for(int n : nums)

Given a nested list of integers represented as a string, implement a parser to deserialize it. Each element is either an integer, or a list – whose elements may also be integers or other lists. Note: You may assume that the string is well-formed: String is non-empty. String does not contain white spaces. String contains only digits 0-9, [, - ,, ]. Example 1: Given s = "324", You should return a NestedInteger object which contains a single integer 324.

Given an array nums, there is a sliding window of size k which is moving from the very left of the array to the very right. You can only see the k numbers in the window. Each time the sliding window moves right by one position. For example, Given nums = [1,3,-1,-3,5,3,6,7], and k = 3. Window position Max --------------- ----- [1 3 -1] -3 5 3 6 7 3 1 [3 -1 -3] 5 3 6 7 3 1 3 [-1 -3 5] 3 6 7 5 1 3 -1 [-3 5 3] 6 7 5 1 3 -1 -3 [5 3 6] 7 6 1 3 -1 -3 5 [3 6 7] 7 Therefore, return the max sliding window as [3,3,5,5,6,7].

Given a n x n matrix where each of the rows and columns are sorted in ascending order, find the kth smallest element in the matrix. Note that it is the kth smallest element in the sorted order, not the kth distinct element. Example: matrix = [ [ 1, 5, 9], [10, 11, 13], [12, 13, 15] ], k = 8, return 13. Note: You may assume k is always valid, 1 ≤ k ≤ n2.

You are given two integer arrays nums1 and nums2 sorted in ascending order and an integer k. Define a pair (u,v) which consists of one element from the first array and one element from the second array. Find the k pairs (u1,v1),(u2,v2) …(uk,vk) with the smallest sums. Example 1: Given nums1 = [1,7,11], nums2 = [2,4,6], k = 3 Return: [1,2],[1,4],[1,6] The first 3 pairs are returned from the sequence:

The gray code is a binary numeral system where two successive values differ in only one bit. Given a non-negative integer n representing the total number of bits in the code, print the sequence of gray code. A gray code sequence must begin with 0. For example, given n = 2, return [0,1,3,2]. Its gray code sequence is: 00 - 0 01 - 1 11 - 3 10 - 2 Note: For a given n, a gray code sequence is not uniquely defined.

Given a positive integer num, write a function which returns True if num is a perfect square else False. Note: Do not use any built-in library function such as sqrt. Example 1: Input: 16 Returns: True Example 2: Input: 14 Returns: False Solution: public class Solution { public boolean isPerfectSquare(int num) { long x = num; while(x*x>num){ x = (x+num/x)/2; } return x*x==num; } }

Given a binary tree, imagine yourself standing on the right side of it, return the values of the nodes you can see ordered from top to bottom. For example: Given the following binary tree, 1 <--- / \ 2 3 <--- \ \ 5 4 <--- You should return [1, 3, 4]. Solution: /** * Definition for a binary tree node. * public class TreeNode { * int val; *