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소스 코드는 여기 있습니다. 문제는 여기 있습니다. Problem Given an integer n, return true if it is a power of three. Otherwise, return false. An integer n is a power of three, if there exists an integer x such that n == 3^x. Example 1: Input: n = 27 Output: true Example 2: Input: n = 0 Output: false Example 3: Input: n = 9 Output: true Solution 3의 n제곱인 경우 true를 반환하는 문제입니다. public class Solution { public boolean isPo..

소스 코드는 여기 있습니다. 문제는 여기 있습니다. Problem Given an integer n, return true if it is a power of four. Otherwise, return false. An integer n is a power of four, if there exists an integer x such that n == 4x. Example 1: Input: n = 16 Output: true Example 2: Input: n = 5 Output: false Example 3: Input: n = 1 Output: true Constraints: -2^31 >= 1; // 오른쪽으로 한 칸 bit shift } return numberOfOnes == 1 && (numbe..

소스 코드는 여기 있습니다. 문제는 여기 있습니다. Problem Given the head of a singly linked list, return true if it is a palindrome. Example 1: Input: head = [1,2,2,1] Output: true Example 2: Input: head = [1,2] Output: false Constraints: The number of nodes in the list is in the range [1, 10^5]. 0 test(ListNode.of(1, 2, 2, 1), true) ); } private void test(ListNode given, boolean expected) { // when Solution palindr..

소스 코드는 여기 있습니다. 문제는 여기 있습니다. Problem A car travels from a starting position to a destination which is target miles east of the starting position. There are gas stations along the way. The gas stations are represented as an array stations where stations[i] = [positioni, fueli] indicates that the ith gas station is positioni miles east of the starting position and has fueli liters of gas. The car ..

소스 코드는 여기 있습니다. 문제는 여기 있습니다. Problem 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. Example 1: Input: arr = [3,3,3,3,5,5,5,2,2,7] Output: 2 Explanation: Choosing {3,7} will make the new array [5,5,5,2,2] which has ..

소스 코드는 여기 있습니다. 문제는 여기 있습니다. Problem 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: [".-","-...","-.-.","-..",".","..-.","--.","....","..",".---","-.-",".-..","..

소스 코드는 여기 있습니다. 문제는 여기 있습니다. Problem Given a string s, find the first non-repeating character in it and return its index. If it does not exist, return -1. Example 1: Input: s = "leetcode" Output: 0 Example 2: Input: s = "loveleetcode" Output: 2 Example 3: Input: s = "aabb" Output: -1 Constraints: 1 test("loveleetcode", 2), () -> test("aabb", -1) ); } private void test(String given, int expected)..

소스 코드는 여기 있습니다. 문제는 여기 있습니다. Problem Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M. Symbol Value I 1 V 5 X 10 L 50 C 100 D 500 M 1000 For example, 2 is written as II in Roman numeral, just two ones added together. 12 is written as XII, which is simply X + II. The number 27 is written as XXVII, which is XX + V + II. Roman numerals are usually written largest to..

소스 코드는 여기 있습니다. 문제는 여기 있습니다. Problem Given a binary search tree (BST), find the lowest common ancestor (LCA) node of two given nodes in the BST. According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between two nodes p and q as the lowest node in T that has both p and q as descendants (where we allow a node to be a descendant of itself).” Example 1: Input: root ..

소스 코드는 여기 있습니다. 문제는 여기 있습니다. Problem 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 also be binary search tr..