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문제 링크: https://leetcode.com/problems/reduce-array-size-to-the-half/ 문제 You are given an integer array arr. You can choose a set of integers and remove all the occurrences of these integers in the array. Return the minimum size of the set so that at least half of the integers of the array are removed. 조건 2

문제 링크: https://leetcode.com/problems/unique-morse-code-words/ 문제 International Morse Code defines a standard encoding where each letter is mapped to a series of dots and dashes, as follows: 'a' maps to ".-", 'b' maps to "-...", 'c' maps to "-.-.", and so on. For convenience, the full table for the 26 letters of the English alphabet is given below: [".-","-...","-.-.","-..",".","..-.","--.","......

문제 링크: https://leetcode.com/problems/first-unique-character-in-a-string/ 문제 Given a string s, find the first non-repeating character in it and return its index. If it does not exist, return -1. 조건 1

문제 링크: https://leetcode.com/problems/validate-binary-search-tree/ 문제 Given the root of a binary tree, determine if it is a valid binary search tree (BST). A valid BST is defined as follows: The left subtree of a node contains only nodes with keys less than the node's key. The right subtree of a node contains only nodes with keys greater than the node's key. Both the left and right subtrees must ..

문제 링크: https://leetcode.com/problems/convert-sorted-array-to-binary-search-tree/ 문제 Given an integer array nums where the elements are sorted in ascending order, convert it to a height-balanced binary search tree. A height-balanced binary tree is a binary tree in which the depth of the two subtrees of every node never differs by more than one. 조건 1

문제 링크: https://leetcode.com/problems/binary-trees-with-factors/ 문제 Given an array of unique integers, arr, where each integer arr[i] is strictly greater than 1. We make a binary tree using these integers, and each number may be used for any number of times. Each non-leaf node's value should be equal to the product of the values of its children. Return the number of binary trees we can make. The ..

문제 링크: https://leetcode.com/problems/longest-increasing-subsequence/ 문제 Given an integer array nums, return the length of the longest strictly increasing subsequence. A subsequence is a sequence that can be derived from an array by deleting some or no elements without changing the order of the remaining elements. For example, [3,6,2,7] is a subsequence of the array [0,3,1,6,2,2,7]. 조건 1

문제 링크: https://leetcode.com/problems/combination-sum-iv/ 문제 Given an array of distinct integers nums and a target integer target, return the number of possible combinations that add up to target. The test cases are generated so that the answer can fit in a 32-bit integer. 조건 1