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Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid. An input string is valid if: Open brackets must be closed by the same type of brackets. Open brackets must be closed in the correct order. Note that an empty string is also considered valid. Example 1: Input: "()" Output: true Example 2: Input: "()[]{}" Output: true Example 3: I..

Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases. Note: For the purpose of this problem, we define empty string as valid palindrome. Example 1: Input: "A man, a plan, a canal: Panama" Output: true Example 2: Input: "race a car" Output: false Solution import re class Solution: def isPalindrome(self, s: str) -> bool: s = s.lower() text = ..

Given a string, find the first non-repeating character in it and return it's index. If it doesn't exist, return -1. Examples: s = "leetcode" return 0. s = "loveleetcode", return 2. Solution from collections import Counter class Solution: def firstUniqChar(self, s: str) -> int: answer = -1 s = list(s) cnt_dict = Counter(s) i = 0 for word in s: if cnt_dict[word] == 1: answer = i break i = i + 1 re..

Given two sorted integer arrays nums1 and nums2, merge nums2 into nums1 as one sorted array. Note: The number of elements initialized in nums1 and nums2 are m and n respectively. You may assume that nums1 has enough space (size that is greater or equal to m + n) to hold additional elements from nums2. Example: Input: nums1 = [1,2,3,0,0,0], m = 3 nums2 = [2,5,6], n = 3 Output: [1,2,2,3,5,6] Solut..

Given a non-empty array of integers, every element appears twice except for one. Find that single one. Note: Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory? Example 1: Input: [2,2,1] Output: 1 Example 2: Input: [4,1,2,1,2] Output: 4 Solution from collections import Counter class Solution: def singleNumber(self, nums: List[int]) -> int: c..

Write a program that outputs the string representation of numbers from 1 to n. But for multiples of three it should output “Fizz” instead of the number and for the multiples of five output “Buzz”. For numbers which are multiples of both three and five output “FizzBuzz”. Example: n = 15, Return: [ "1", "2", "Fizz", "4", "Buzz", "Fizz", "7", "8", "Fizz", "Buzz", "11", "Fizz", "13", "14", "FizzBuzz..

Given an array of integers A, consider all non-empty subsequences of A. For any sequence S, let the width of S be the difference between the maximum and minimum element of S. Return the sum of the widths of all subsequences of A. As the answer may be very large, return the answer modulo 10^9 + 7. Example 1: Input: [2,1,3] Output: 6 Explanation: Subsequences are [1], [2], [3], [2,1], [2,3], [1,3]..

Given an array containing n distinct numbers taken from 0, 1, 2, ..., n, find the one that is missing from the array. Example 1: Input: [3,0,1] Output: 2 Example 2: Input: [9,6,4,2,3,5,7,0,1] Output: 8 Note: Your algorithm should run in linear runtime complexity. Could you implement it using only constant extra space complexity? Solution class Solution: def missingNumber(self, nums: List[int]) -..

Write a function that reverses a string. The input string is given as an array of characters char[]. Do not allocate extra space for another array, you must do this by modifying the input array in-place with O(1) extra memory. You may assume all the characters consist of printable ascii characters. Example 1: Input: ["h","e","l","l","o"] Output: ["o","l","l","e","h"] Example 2: Input: ["H","a","..

Given an integer, write a function to determine if it is a power of three. Example 1: Input: 27 Output: true Example 2: Input: 0 Output: false Example 3: Input: 9 Output: true Example 4: Input: 45 Output: false Follow up: Could you do it without using any loop / recursion? Solution class Solution: def isPowerOfThree(self, n: int) -> bool: return n > 0 and pow(3, 31, n) == 0 SOMJANG/CODINGTEST_PR..

Count the number of prime numbers less than a non-negative number, n. Example: Input: 10 Output: 4 Explanation: There are 4 prime numbers less than 10, they are 2, 3, 5, 7. Solution class Solution: def getPrimaryNum_Eratos(N): nums = [True] * (N + 1) for i in range(2, len(nums) // 2 + 1): if nums[i] == True: for j in range(i+i, N, i): nums[j] = False return [i for i in range(2, N) if nums[i] == ..

Given two integers dividend and divisor, divide two integers without using multiplication, division and mod operator. Return the quotient after dividing dividend by divisor. The integer division should truncate toward zero, which means losing its fractional part. For example, truncate(8.345) = 8 and truncate(-2.7335) = -2. Example 1: Input: dividend = 10, divisor = 3 Output: 3 Explanation: 10/3 ..

Given a collection of distinct integers, return all possible permutations. Example: Input: [1,2,3] Output: [ [1,2,3], [1,3,2], [2,1,3], [2,3,1], [3,1,2], [3,2,1] ] Solution from itertools import permutations class Solution: def permute(self, nums: List[int]) -> List[List[int]]: permu = list(permutations(nums, len(nums))) return permu SOMJANG/CODINGTEST_PRACTICE 1일 1문제 since 2020.02.07. Contribut..

Given an array with n objects colored red, white or blue, sort them in-place so that objects of the same color are adjacent, with the colors in the order red, white and blue. Here, we will use the integers 0, 1, and 2 to represent the color red, white, and blue respectively. Note: You are not suppose to use the library's sort function for this problem. Example: Input: [2,0,2,1,1,0] Output: [0,0,..

Implement pow(x, n), which calculates x raised to the power n (x^n). Example 1: Input: 2.00000, 10 Output: 1024.00000 Example 2: Input: 2.10000, 3 Output: 9.26100 Example 3: Input: 2.00000, -2 Output: 0.25000 Explanation: 2-2 = 1/22 = 1/4 = 0.25 Note: -100.0 float: my_pow_num = pow(x, n) if my_pow_num > (pow(2, 31) - 1): my_pow_num = pow(2, 31) -1 elif my_pow_num < (pow(2, 31)) * (-1): my_pow_nu..

Given a non-empty array of digits representing a non-negative integer, plus one to the integer. The digits are stored such that the most significant digit is at the head of the list, and each element in the array contain a single digit. You may assume the integer does not contain any leading zero, except the number 0 itself. Example 1: Input: [1,2,3] Output: [1,2,4] Explanation: The array repres..

Implement int sqrt(int x). Compute and return the square root of x, where x is guaranteed to be a non-negative integer. Since the return type is an integer, the decimal digits are truncated and only the integer part of the result is returned. Example 1: Input: 4 Output: 2 Example 2: Input: 8 Output: 2 Explanation: The square root of 8 is 2.82842..., and since the decimal part is truncated, 2 is ..

Implementatoiwhich converts a string to an integer. The function first discards as many whitespace characters as necessary until the first non-whitespace character is found. Then, starting from this character, takes an optional initial plus or minus sign followed by as many numerical digits as possible, and interprets them as a numerical value. The string can contain additional characters after ..

The string "PAYPALISHIRING" is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font for better legibility) P A H N A P L S I I G Y I R And then read line by line: "PAHNAPLSIIGYIR" Write the code that will take a string and make this conversion given a number of rows: string convert(string s, int numRows); Example 1: Input: s = "PA..

Given a string, find the length of the longest substring without repeating characters. Example 1: Input: "abcabcbb" Output: 3 Explanation: The answer is "abc", with the length of 3. Example 2: Input: "bbbbb" Output: 1 Explanation: The answer is "b", with the length of 1. Example 3: Input: "pwwkew" Output: 3 Explanation: The answer is "wke", with the length of 3. Note that the answer must be a su..

Given a string, you need to reverse the order of characters in each word within a sentence while still preserving whitespace and initial word order. Example 1: Input: "Let's take LeetCode contest" Output: "s'teL ekat edoCteeL tsetnoc" Note: In the string, each word is separated by single space and there will not be any extra space in the string. Solution 1 class Solution: def reverseWords(self, ..

Every email consists of a local name and a domain name, separated by the @ sign. For example, in alice@leetcode.com, alice is the local name, and leetcode.com is the domain name. Besides lowercase letters, these emails may contain '.'s or '+'s. If you add periods ('.') between some characters in the local name part of an email address, mail sent there will be forwarded to the same address withou..

Given a string s consists of upper/lower-case alphabets and empty space characters ' ', return the length of last word (last word means the last appearing word if we loop from left to right) in the string. If the last word does not exist, return 0. Note: A word is defined as a maximal substring consisting of non-space characters only. Example: Input: "Hello World" Output: 5 Solution class Soluti..

Given a non-empty array of integers, return the third maximum number in this array. If it does not exist, return the maximum number. The time complexity must be in O(n). Example 1: Input: [3, 2, 1] Output: 1 Explanation: The third maximum is 1. Example 2: Input: [1, 2] Output: 2 Explanation: The third maximum does not exist, so the maximum (2) is returned instead. Example 3: Input: [2, 2, 3, 1] ..

Given an input string, reverse the string word by word. Example 1: Input: "the sky is blue" Output: "blue is sky the" Example 2: Input: " hello world! " Output: "world! hello" Explanation: Your reversed string should not contain leading or trailing spaces. Example 3: Input: "a good example" Output: "example good a" Explanation: You need to reduce multiple spaces between two words to a single spa..

There are two sorted arrays nums1 and nums2 of size m and n respectively. Find the median of the two sorted arrays. The overall run time complexity should be O(log (m+n)). You may assume nums1 and nums2 cannot be both empty. Example 1: nums1 = [1, 3] nums2 = [2] The median is 2.0 Example 2: nums1 = [1, 2] nums2 = [3, 4] The median is (2 + 3)/2 = 2.5 Solution class Solution: def findMedianSortedA..

1일 1문제 15일차! 오늘의 문제는 leetCode의 Add Two Numbers 입니다. idEANS 팀원들과 공부하기로한 알고리즘 공부를 위해 푼 문제로 팀 블로그에 포스팅 해 두었습니다. Leetcode#1_Add Two Numbers_02w03 by SOMJANG 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 retur.. ideans.tistory.com

1일 1문제 14일차! 14일차의 문제는 leetCode의 Reverse Integer입니다. idEANS 팀원들과 공부하기로한 알고리즘 공부를 위해 푼 문제로 팀 블로그에 포스팅 해 두었습니다. Leetcode#1_Reverse Integer_02w03 by SOMJANG Given a 32-bit signed integer, reverse digits of an integer. Example 1 Input: 123 Output: 321 Example 2 Input: -123 Output: -321 Example 3 Input: 120 Output: 21 Note: Assume we are dealing with an.. ideans.tistory.com