수 많은 우문은 현답을 만든다

문제 Given a binary tree, determine if it is height-balanced Example 1: Input: root = [3,9,20,null,null,15,7] Output: true Example 2: Input: root = [1,2,2,3,3,null,null,4,4] Output: false Example 3: Input: root = [] Output: true 풀이 더보기 class Solution: def isBalanced(self, root: Optional[TreeNode]) -> bool: def balance(node): if not node: return 0 left = balance(node.left) right = balance(node.righ..

문제 You are given the heads of two sorted linked lists list1 and list2. Merge the two lists in a one sorted list. The list should be made by splicing together the nodes of the first two lists. Return the head of the merged linked list. Example 1: Input: list1 = [1,2,4], list2 = [1,3,4] Output: [1,1,2,3,4,4] Example 2: Input: list1 = [], list2 = [] Output: [] Example 3: Input: list1 = [], list2 = ..

문제 Given the head of a singly linked list, reverse the list, and return the reversed list. 우선 구조를 파악하고 코딩해보자. head의 구조는 어떻게 생겼을까? 펼치기 더보기 head : ListNode{val:1, next:ListNode{val:2, next: None}} 그럼 head는 어떻게 선언을 했을까? 이해를 위해 역으로 생각보자. 펼치기 더보기 head = ListNode(1) head.next = ListNode(2) head.next.next = ListNode(3) 풀이 더보기 # Definition for singly-linked list. # class ListNode: # def __init__(self, v..

Given a string s 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. Every close bracket has a corresponding open bracket of the same type. Example 1: Input: s = "()" Output: true Example 2: Input: s = "()[]..