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# Nth Digit

Nth DigitFind the nth digit of the infinite integer sequence 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, … Note: n is positive and will fit within the range of a 32-bit signed integer (n < 231). Example 1:

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# Valid Perfect Square

Valid Perfect SquareGiven 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 1:12

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# Sum of Two Integers

Sum of Two IntegersCalculate the sum of two integers a and b, but you are not allowed to use the operator + and -. For Example:1Given a = 1 and b = 2, return 3. 提示 解題應用 BitManipulation XOR,AND

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# Reverse Vowels of a String

Reverse Vowels of a StringWrite a function that takes a string as input and reverse only the vowels of a string. Example1:1Given s = "hello", return "holle". Example 2:1Given s =

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# Ransom Note

Ransom NoteGiven an arbitrary ransom note string and another string containing letters from all the magazines, write a function that will return true if the ransom note can be constructed from the ma

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# Intersection of Two Arrays

Intersection of Two ArraysGiven two arrays, write a function to compute their intersection. ###For Example: 1Given nums1 = [1, 2, 2, 1], nums2 = [2, 2], return . Note: Each element in the result

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# Intersection of Two Arrays II

Intersection of Two Arrays IIGiven two arrays, write a function to compute their intersection. For Example:1Given nums1 = [1, 2, 2, 1], nums2 = [2, 2], return [2, 2]. Note: Each element in the resul

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# First Unique Character in a String

First Unique Character in a StringGiven a string, find the first non-repeating character in it and return it’s index. If it doesn’t exist, return -1. For Examples:12345s = "leetcode"return

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# Reverse String

Reverse StringWrite a function that takes a string as input and returns the string reversed. For Example:1Given s = "hello", return "olleh". 提示 解題應用 TwoPointers String D

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# Power of Four

Power of FourGiven an integer (signed 32 bits), write a function to check whether it is a power of 4. For Example:1Given num = 16, return true. Given num = 5, return false. Follow up: Could you solve

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# Power of Three

Power of ThreeGiven an integer, write a function to determine if it is a power of three. Follow up: Could you do it without using any loop / recursion? 提示 解題應用 Math 腦力激盪 Default:123func isP

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# Range Sum Query - Immutable

Range Sum Query - ImmutableGiven an integer array nums, find the sum of the elements between indices i and j (i ≤ j), inclusive. For Example:12345Given nums = [-2, 0, 3, -5, 2, -1]sumRange(0, 2) ->

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# Nim Game

Nim GameYou are playing the following Nim Game with your friend: There is a heap of stones on the table, each time one of you take turns to remove 1 to 3 stones. The one who removes the last stone wi

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# Word Pattern

Word PatternGiven a pattern and a string str, find if str follows the same pattern. Here follow means a full match, such that there is a bijection between a letter in pattern and a non-empty word in

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# Move Zeroes

Move ZeroesGiven an array nums, write a function to move all 0’s to the end of it while maintaining the relative order of the non-zero elements. For example:1Given nums = [0, 1, 0, 3, 12], after call

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# Missing Number

Missing NumberGiven an array containing n distinct numbers taken from 0, 1, 2, …, n, find the one that is missing from the array. For example:1Given nums = [0, 1, 3] return 2. Note: Your algorithm sh

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# Ugly Number

Ugly NumberWrite a program to check whether a given number is an ugly number. Ugly numbers are positive numbers whose prime factors only include 2, 3, 5. For example, 6, 8 are ugly while 14 is not ug

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Add DigitsGiven a non-negative integer num, repeatedly add all its digits until the result has only one digit. For example:1Given num = 38, the process is like: 3 + 8 = 11, 1 + 1 = 2. Since 2 has onl

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# Binary Tree Paths

Binary Tree PathsGiven a binary tree, return all root-to-leaf paths. For example, given the following binary tree: 12345 1 / \2 3 \ 5 All root-to-leaf paths are: 1["1->2->5",

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Palindrome Linked ListGiven two strings s and t, write a function to determine if t is an anagram of s. For example:12s = "anagram", t = "nagaram", return true.s = "rat"

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