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LeetCode 41. First Missing Positive Problem: Given an unsorted integer array, find the smallest missing positive integer. Example 1: Input: [1,2,0] Output: 3 Example 2: Input: [3,4,-1,1] Output: 2 Example 3: Input: [7,8,9,11,12] Output: 1 -Summary- 1. Set first positive integer as 1 --> posNum 2. loop-through the nums and check if posNum is in the nums list. (max int: 2^31 -1) - if there is, adding 1 more value to posNum and find .. 2020. 6. 18.
LeetCode.Surrounded Regions Problem: Given a 2D board containing 'X' and 'O' (the letter O), capture all regions surrounded by 'X'. A region is captured by flipping all 'O's into 'X's in that surrounded region. Example: Explanation: Surrounded regions shouldn’t be on the border, which means that any 'O' on the border of the board are not flipped to 'X'. Any 'O' that is not on the border and it is not connected to an 'O' on.. 2020. 6. 18.
LeetCode 665. Non-decreasing Array Problem: Given an array nums with n integers, your task is to check if it could become non-decreasing by modifying at most 1 element. We define an array is non-decreasing if nums[i] 2020. 6. 18.
LeetCode.Hamming Distance [Bit] Problem: The Hamming distance between two integers is the number of positions at which the corresponding bits are different. Given two integers x and y, calculate the Hamming distance. Note: 0 ≤ x, y < 231. Example: Input: x = 1, y = 4 Output: 2 Explanation: 1 (0 0 0 1) 4 (0 1 0 0) ↑ ↑ The above arrows point to positions where the corresponding bits are different. -Summary- Used bin() method and.. 2020. 6. 18.
LeetCode 136. Single Number Problem: 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 -Summary- Using XOR Bit operation 1. Do XOR bit operation for all numbers 2. return the answer EX.. 2020. 6. 17.
LeetCode. Validate IP Address Problem: Write a function to check whether an input string is a valid IPv4 address or IPv6 address or neither. IPv4 addresses are canonically represented in dot-decimal notation, which consists of four decimal numbers, each ranging from 0 to 255, separated by dots ("."), e.g.,172.16.254.1; Besides, leading zeros in the IPv4 is invalid. For example, the address 172.16.254.01 is invalid. IPv6 addr.. 2020. 6. 17.

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