언클린 코더

1. 문제(원본) Given an array of 2n integers, your task is to group these integers into n pairs of integer, say (a1, b1), (a2, b2), ..., (an, bn) which makes sum of min(ai, bi) for all i from 1 to n as large as possible. Example 1: Input: [1,4,3,2] Output: 4 Explanation: n is 2, and the maximum sum of pairs is 4 = min(1, 2) + min(3, 4). Note: n is a positive integer, which is in the range of [1, 1000..

1. 문제(원본) Students are asked to stand in non-decreasing order of heights for an annual photo. Return the minimum number of students that must move in order for all students to be standing in non-decreasing order of height. Notice that when a group of students is selected they can reorder in any possible way between themselves and the non selected students remain on their seats. Example 1: Input:..

1. 문제(원본) A self-dividing number is a number that is divisible by every digit it contains. For example, 128 is a self-dividing number because 128 % 1 == 0, 128 % 2 == 0, and 128 % 8 == 0. Also, a self-dividing number is not allowed to contain the digit zero. Given a lower and upper number bound, output a list of every possible self dividing number, including the bounds if possible. Example 1: In..

1. 문제(원본) Given the root node of a binary search tree (BST) and a value. You need to find the node in the BST that the node's value equals the given value. Return the subtree rooted with that node. If such node doesn't exist, you should return NULL. In the example above, if we want to search the value 5, since there is no node with value 5, we should return NULL. Note that an empty tree is repre..

1. 문제(원본) In a array A of size 2N, there are N+1 unique elements, and exactly one of these elements is repeated N times. Return the element repeated N times. Example 1: Input: [1,2,3,3] Output: 3 Example 2: Input: [2,1,2,5,3,2] Output: 2 Example 3: Input: [5,1,5,2,5,3,5,4] Output: 5 Note: 4 Int { let mappedItems = A.map { ($0, 1) } let counts = Dictionary(mappedItems, uniquingKeysWith: +) // key..

1. 문제(원본) Given two binary trees and imagine that when you put one of them to cover the other, some nodes of the two trees are overlapped while the others are not. You need to merge them into a new binary tree. The merge rule is that if two nodes overlap, then sum node values up as the new value of the merged node. Otherwise, the NOT null node will be used as the node of new tree. Note: The merg..

1. 문제(원본) There is a robot starting at position (0, 0), the origin, on a 2D plane. Given a sequence of its moves, judge if this robot ends up at (0, 0) after it completes its moves. The move sequence is represented by a string, and the character moves[i] represents its ith move. Valid moves are R (right), L (left), U (up), and D (down). If the robot returns to the origin after it finishes all of..

저번에 테이블 뷰에 커스텀 셀을 적용하는 방법을 해보았었는데 이번에는 컬렉션 뷰를 사용해서 같은 방식으로 커스텀 셀을 적용해 보겠습니다. 컬렉션 뷰는 테이블 뷰보다 좀 더 난이도가 있다고 생각합니다. (이것저것 조절해야 할 것도 많습니다...) 그래도 잘 활용할 줄만 안다면 자신의 App의 표현력을 높일 수 있을 것이라고 생각합니다. 구성은 거의 테이블 뷰와 비슷합니다. 그렇다면 한 번 알아보겠습니다. 1. Storyboard에 CollectionView 생성 storyboard에서 collectionView를 생성합니다. 아래와 같이 좌상단에 조그만 사각형 셀이 보입니다. 하지만 이번에 해보는 것은 커스텀 셀이기 때문에 그냥 넘기겠습니다. 2. CollectionView 설정 최소한의 기능을 사용하여 ..

1. 문제(원본) On a plane there are n points with integer coordinates points[i] = [xi, yi]. Your task is to find the minimum time in seconds to visit all points. You can move according to the next rules: In one second always you can either move vertically, horizontally by one unit or diagonally (it means to move one unit vertically and one unit horizontally in one second). You have to visit the point..

1. 문제(원본) Given head which is a reference node to a singly-linked list. The value of each node in the linked list is either 0 or 1. The linked list holds the binary representation of a number. Return the decimal value of the number in the linked list. Example 1: Input: head = [1,0,1] Output: 5 Explanation: (101) in base 2 = (5) in base 10 Example 2: Input: head = [0] Output: 0 Example 3: Input: ..