내 맘대로 알고리즘
May LeetCoding Challenge[Day3] - Ransom Note
Given 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 magazines ; otherwise, it will return false. Each letter in the magazine string can only be used once in your ransom note. Note:You may assume that both strings contain only lowercase letters. canConstruct("a", "..
May LeetCoding Challenge[Day2] - Jewels and Stones
You're given strings J representing the types of stones that are jewels, and S representing the stones you have. Each character in S is a type of stone you have. You want to know how many of the stones you have are also jewels. The letters in J are guaranteed distinct, and all characters in J and S are letters. Letters are case sensitive, so "a" is considered a different type of stone from "A". ..
May LeetCoding Challenge[Day1] - First Bad Version
You are a product manager and currently leading a team to develop a new product. Unfortunately, the latest version of your product fails the quality check. Since each version is developed based on the previous version, all the versions after a bad version are also bad. Suppose you have n versions [1, 2, ..., n] and you want to find out the first bad one, which causes all the following ones to be..
Leetcode[day20] - Construct Binary Search Tree from Preorder Traversal
Return the root node of a binary search tree that matches the given preorder traversal. (Recall that a binary search tree is a binary tree where for every node, any descendant of node.left has a value node.val. Also recall that a preorder traversal displays the value of the node first, then traverses node.left, then traverses node.right.) It's guaranteed that for the given test cases there is al..
Leetcode[day19] -Search in Rotated Sorted Array
Suppose an array sorted in ascending order is rotated at some pivot unknown to you beforehand. (i.e., [0,1,2,4,5,6,7] might become [4,5,6,7,0,1,2]). You are given a target value to search. If found in the array return its index, otherwise return -1. You may assume no duplicate exists in the array. Your algorithm's runtime complexity must be in the order of O(log n). Input: nums = [4,5,6,7,0,1,2]..
Leetcode[day18] - Minimum Path Sum
Given a m x n grid filled with non-negative numbers, find a path from top left to bottom right which minimizes the sum of all numbers along its path. Note: You can only move either down or right at any point in time. Input: [ [1,3,1], [1,5,1], [4,2,1] ] Output: 7 Explanation: Because the path 1→3→1→1→1 minimizes the sum. 1. 알고리즘을 해결하기 위해서 생각한 방법 - 최소값을 구해야하니, Math.min()을 활용해야 한다고 생각이 들었다. - 누적된 ..
Leetcode[day17] - Number of Islands
Given a 2d grid map of '1's (land) and '0's (water), count the number of islands. An island is surrounded by water and is formed by connecting adjacent lands horizontally or vertically. You may assume all four edges of the grid are all surrounded by water. Example 1: Input: 11110 11010 11000 00000 Output: 1 1. 알고리즘을 해결하기 위해서 생각한 방법 - 우선, 문제를 이해하는데 시간이 좀 걸렸다. - 해당 문제는 0이 물이고, 1이 땅이라고 할 때, 이어진 1이 ..
Leetcode[day16] - Valid Parenthesis String
Given a string containing only three types of characters: '(', ')' and '*', write a function to check whether this string is valid. We define the validity of a string by these rules: 1. Any left parenthesis '(' must have a corresponding right parenthesis ')'. 2. Any right parenthesis ')' must have a corresponding left parenthesis '('. 3. Left parenthesis '(' must go before the corresponding righ..