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알고리즘 문제풀이/leetcode142

[leetcode 114] Flatten Binary Tree to Linked List Given a binary tree, flatten it to a linked list in-place. For example, given the following tree: 문제 풀이: - 순서가 root->left->right 순서: preorder임 - 스택을 사용해서 preorder 순회하기 /** * Definition for a binary tree node. * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode() : val(0), left(nullptr), right(nullptr) {} * TreeNode(int x) : val(x), left(nullptr), right(nullptr) {} * Tr.. 2020. 10. 21.
[leetcode 136] Single Number Given a non-empty array of integers nums, every element appears twice except for one. Find that single one. Follow up: Could you implement a solution with a linear runtime complexity and without using extra memory? 한 번만 등장한 원소 찾기 Example 1: Input: nums = [2,2,1] Output: 1 Example 2: Input: nums = [4,1,2,1,2] Output: 4 Example 3: Input: nums = [1] Output: 1 문제 풀이: - follow up을 무시하고 map으로 풀면 쉽게 풀린.. 2020. 10. 21.
[leetcode 138] Copy List with Random Pointer A linked list is given such that each node contains an additional random pointer which could point to any node in the list or null. Return a deep copy of the list. The Linked List is represented in the input/output as a list of n nodes. Each node is represented as a pair of [val, random_index] where: val: an integer representing Node.val random_index: the index of the node (range from 0 to n-1) .. 2020. 10. 21.
[leetcode 240] Search a 2D Matrix II Write an efficient algorithm that searches for a value in an m x n matrix. This matrix has the following properties: Integers in each row are sorted in ascending from left to right. Integers in each column are sorted in ascending from top to bottom. 위 조건을 만족하는 이차원 배열에서 target값을 찾기 Example: Consider the following matrix: [ [1, 4, 7, 11, 15], [2, 5, 8, 12, 19], [3, 6, 9, 16, 22], [10, 13, 14, 17, .. 2020. 10. 20.

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