There are several cards arranged in a row, and each card has an associated number of points. The points are given in the integer array cardPoints. In one step, you can take one card from the beginning or from the end of the row. You have to take exactly k cards. Your score is the sum of the points of the cards you have taken. ...
You are given an integer n, which indicates that there are n courses labeled from 1 to n. You are also given an array relations where relations[i] = [prevCoursei, nextCoursei], representing a prerequisite relationship between course prevCoursei and course nextCoursei: course prevCoursei has to be taken before course nextCoursei. In one semester, you can take any number of courses as long as you have taken all the prerequisites in the previous semester for the courses you are taking. ...
Given a n * n matrix grid of 0’s and 1’s only. We want to represent the grid with a Quad-Tree. Return the root of the Quad-Tree representing the grid. Notice that you can assign the value of a node to True or False when isLeaf is False, and both are accepted in the answer. A Quad-Tree is a tree data structure in which each internal node has exactly four children. Besides, each node has two attributes: ...
You are given an n x n 2D matrix representing an image, rotate the image by 90 degrees (clockwise). You have to rotate the image in-place, which means you have to modify the input 2D matrix directly. DO NOT allocate another 2D matrix and do the rotation. Example 1: Input: matrix = [[1,2,3],[4,5,6],[7,8,9]] Output: [[7,4,1],[8,5,2],[9,6,3]] Example 2: Input: matrix = [[5,1,9,11],[2,4,8,10],[13,3,6,7],[15,14,12,16]] Output: [[15,13,2,5],[14,3,4,1],[12,6,8,9],[16,7,10,11]] Example 3: Input: matrix = [[1]] Output: [[1]] Example 4: Input: matrix = [[1,2],[3,4]] Output: [[3,1],[4,2]] Constraints: ...
Given the root of a binary tree, construct a 0-indexed m x n string matrix res that represents a formatted layout of the tree. The formatted layout matrix should be constructed using the following rules: The height of the tree is height and the number of rows m should be equal to height + 1. The number of columns n should be equal to 2height+1 - 1. Place the root node in the middle of the top row (more formally, at location res[0][(n-1)/2]). For each node that has been placed in the matrix at position res[r][c], place its left child at res[r+1][c-2height-r-1] and its right child at res[r+1][c+2height-r-1]. Continue this process until all the nodes in the tree have been placed. Any empty cells should contain the empty string “”. Return the constructed matrix res. ...
Given a string s, return all the palindromic permutations (without duplicates) of it. You may return the answer in any order. If s has no palindromic permutation, return an empty list. Example 1: Input: s = "aabb" Output: ["abba","baab"] Example 2: Input: s = "abc" Output: [] Constraints: 1 <= s.length <= 16 s consists of only lowercase English letters. Solution class Solution { public List<String> generatePalindromes(String s) { Set<String> res = new HashSet<>(); int[] freq = new int[256]; int count = 0; for (char c : s.toCharArray()) { freq[c]++; } if (!canPermute(freq)) { return Collections.emptyList(); } char mid = ' '; int k = 0; char[] st = new char[s.length() / 2]; for (int i = 0; i < freq.length; i++) { if (freq[i] % 2 == 1) { mid = (char) i; } for (int j = 0; j < freq[i] / 2; j++) { st[k++] = (char) i; } } permute(0, st, mid, res); return new ArrayList<>(res); } void permute(int i, char[] st, char mid, Set<String> res) { if (i == st.length) { String m = ((mid == ' ') ? "": "" + mid); String val = new String(st) + m + new StringBuilder(new String(st)).reverse().toString(); res.add(val); } else { for (int j = i; j < st.length; j++) { swap(i, j, st); permute(i + 1, st, mid, res); swap(i, j, st); } } } boolean canPermute(int[] freq) { int count = 0; for (int f: freq) { count += f % 2; } return count <= 1; } void swap(int i, int j, char[] st) { char t = st[i]; st[i] = st[j]; st[j] = t; } }
You are given an m x n grid rooms initialized with these three possible values. -1 A wall or an obstacle. 0 A gate. INF Infinity means an empty room. We use the value 231 - 1 = 2147483647 to represent INF as you may assume that the distance to a gate is less than 2147483647. Fill each empty room with the distance to its nearest gate. If it is impossible to reach a gate, it should be filled with INF. ...
Given an integer array nums, return the number of longest increasing subsequences. Notice that the sequence has to be strictly increasing. Example 1: Input: nums = [1,3,5,4,7] Output: 2 Explanation: The two longest increasing subsequences are [1, 3, 4, 7] and [1, 3, 5, 7]. Example 2: Input: nums = [2,2,2,2,2] Output: 5 Explanation: The length of longest continuous increasing subsequence is 1, and there are 5 subsequences' length is 1, so output 5. Constraints: ...
Given a pattern and a string s, return true if s matches the pattern. A string s matches a pattern if there is some bijective mapping of single characters to strings such that if each character in pattern is replaced by the string it maps to, then the resulting string is s. A bijective mapping means that no two characters map to the same string, and no character maps to two different strings. ...
We can shift a string by shifting each of its letters to its successive letter. For example, “abc” can be shifted to be “bcd”. We can keep shifting the string to form a sequence. For example, we can keep shifting “abc” to form the sequence: “abc” -> “bcd” -> … -> “xyz”. Given an array of strings strings, group all strings[i] that belong to the same shifting sequence. You may return the answer in any order. ...