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Validate if a given string is numeric.Some examples:"0" => true" 0.1 " => true"abc" => false"1 a" => false"2e10" => trueNote: It is intended for the problem statement to be ambiguous.

Evaluate the value of an arithmetic expression in Reverse Polish Notation.Valid operators are +, -, *, /. Each operand may be an integer or another expression.Some examples: ["2", "1",

package Algorithm;import java.util.HashSet;import java.util.LinkedList;import java.util.Queue;public class WordLadder { public int ladderLength(String start, String end, HashSet dict)

public class Solution { public int lengthOfLongestSubstring(String s) { // Start typing your Java solution below // DO NOT write main() function int start = 0, res = 0; int[] pos = new int

public class Solution {    public boolean isPalindrome(int x) {        // Start typing your Java solution below        // DO NOT write main() function        if(x < 0)            return fals

public class Solution { public int maxArea(int[] height) { // Start typing your Java solution below // DO NOT write main() function int maxArea = 0; int left = 0; int right = height.leng

public class Solution { public int longestValidParentheses(String s) { // Start typing your Java solution below // DO NOT write main() function int len = s.length(); int max = 0; Stack s

public class Solution { public int searchInsert(int[] A, int target) { // Start typing your Java solution below // DO NOT write main() function if(A.length == 0) return 0; int left = 0;

public class Solution { public int firstMissingPositive(int[] A) { // Start typing your Java solution below // DO NOT write main() function int len = A.length; if(len < 1) return 1; f

Given n non-negative integers representing an elevation map where the width of each bar is 1, compute how much water it is able to trap after raining.For example, Given [0,1,0,2,1,0,1,3,2,1,2,1],

Given a string s consists of upper/lower-case alphabets and empty space characters' ', return the length of last word in the string.If the last word does not exist, return 0.Note: A word is defi

Implement int sqrt(int x).Compute and return the square root of x.public class Solution { public int sqrt(int x) { // Start typing your Java solution below // DO NOT write main() function

Given an array of integers, every element appears three times except for one. Find that single one.Note:Your algorithm should have a linear runtime complexity. Could you implement it without using

Pay attention to this one. Passed after several bug fixes.public class Solution { public int threeSumClosest(int[] num, int target) { // Start typing your Java solution below // DO NOT w

public class Solution { public int maxProfit(int[] prices) { // Start typing your Java solution below // DO NOT write main() function if(prices.length == 0) return 0; int profit = 0;

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 gr

Given a 2D binary matrix filled with 0's and 1's, find the largest rectangle containing all ones and return its area.Solution 1. Using Largest Rectangle in Histogram, O(n^2). Great solution... Hav

Follow up for "Remove Duplicates":What if duplicates are allowed at most twice?For example,Given sorted array A = [1,1,1,2,2,3],Your function should return length = 5, and A is now [1,1,2,2,3]

Given a string containing only digits, restore it by returning all possible valid IP address combinations.For example:Given "25525511135",return ["255.255.11.135", "255.255.111.35"]. (Order does

Kadane Algorithm O(n) Not working for all negative number arrayspublic class Solution { public int maxSubArray(int[] A) { // Start typing your Java solution below // DO NOT write main()

public class ValidPalindrome { /** * Given a string, determine if it is a palindrome, considering only * alphanumeric characters and ignoring cases. * * For example, "A man, a plan, a canal

public class Solution { public ArrayList> res; public String end; public int target_length; public ArrayList temp_list; public ArrayList> findLadders(String start, String end, HashSet dict)

Left[i] means for current day i, best buy and sell value between 0~i;right[i] means for current day i, best buy and sell value between i~length-1.public class Solution { public int maxProfit

public class Solution { public int reverse(int x) { // Start typing your Java solution below // DO NOT write main() function boolean neg = false; if (x < 0) { x = -x; neg = tr

public class Solution { public boolean isValid(String s) { // Start typing your Java solution below // DO NOT write main() function Stack stack = new Stack(); for(int i = 0; i < s.length()

dividend = divisor*2^0 + divisor*2^1 + ... + divisor*2^n + mod; (modpublic class Solution { public int divide(int dividend, int divisor) { // Start typing your Java solution below // DO NO

public class Solution { public ArrayList spiralOrder(int[][] matrix) { // Start typing your Java solution below // DO NOT write main() function ArrayList res = new ArrayList(); int m = mat

Given an integer n, generate a square matrix filled with elements from 1 ton2 in spiral order.For example,Given n = 3,You should return the following matrix:[ [ 1, 2, 3 ], [ 8, 9, 4 ], [ 7,

Given a number represented as an array of digits, plus one to the number.public class Solution { public int[] plusOne(int[] digits) { // Start typing your Java solution below // DO NOT wri

Given an array of words and a length L, format the text such that each line has exactlyL characters and is fully (left and right) justified.You should pack your words in a greedy approach; that is

Given an absolute path for a file (Unix-style), simplify it.For example,path = "/home/", => "/home"path = "/a/./b/../../c/", => "/c"Corner Cases:Did you consider the case where path = "/

Given a string S and a string T, find the minimum window in S which will contain all the characters in T in complexity O(n).For example,S = "ADOBECODEBANC"T = "ABC"Minimum window is "BANC".

This solution O(lg(m + n)) is not good for interview. Try kth smallest element solution extension.public class MedianTwoSortedArrays { private double findMedian(int A[], int B[], int left, i

public class Solution { public String convert(String s, int nRows) { // Start typing your Java solution below // DO NOT write main() function StringBuilder sb = new StringBuilder("");

import java.util.Hashtable;public class Solution { public int[] twoSum(int[] numbers, int target) { // Start typing your Java solution below // DO NOT write main() function int[] res = {0,

public class Solution { public ArrayList> threeSum(int[] num) { // Start typing your Java solution below // DO NOT write main() function ArrayList> res = new ArrayList>(); if(num.length ==

public class Solution { public int maxProfit(int[] prices) { // Start typing your Java solution below // DO NOT write main() function if (prices.length < 2) return 0; int profit = 0;

O(n^2)public class Solution { public String longestPalindrome(String s) { // Start typing your Java solution below // DO NOT write main() function int len = s.length(); if(len == 0)

public class Solution { public int atoi(String str) { // Start typing your Java solution below // DO NOT write main() function if (str == null || str.length() == 0) return 0; int index

public class Solution { public String longestCommonPrefix(String[] strs) { // Start typing your Java solution below // DO NOT write main() function if (strs.length == 0) return ""; for